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Split 18 lb rib roast or cook whole?

I am making a 18 lb standing rib roast for Christmas Eve dinner. Wondering if I should split into 2 more manageable pieces for quicker cooking or leave whole? Any ideas how long a 18 pounder would take if I choose to go that path?


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  1. Can you get the beast in the oven without whacking it?

    9 Replies
    1. re: sarge

      That's my question too. If you can get the whole thing in the oven, I say leave it whole.

      Once you get to a certain size it won't really matter if you cut it in half or not. Just because it weighs more as a single item doesn't necessarily meat it will cook in miraculously shorter time if you chop it in half. You're not adding any distance between the outside and the inside of the meat by adding pounds (compared to say a turkey), you're simply adding length to the item.

      With that said, you might want 2 separate rib roasts so you can have one on one end of the table and one on another end.

      Please, please, PLEEEASE use a probe thermometer for this venture. I assume you've spent well over $100 for this cut of meat and it would be absolutely and completely disastrous if you over cooked it. A probe thermometer will guarantee that the the item won't over cook in any way. It is well worth an extra $20 to get one of these thermometers; consider it a present to yourself!


      The cooking time will vary greatly depending on how hot your oven temp is. I suggest a lower temperature (usually less than 300 F) for the majority of the cooking time. You will end up with a more tender cut of meat and a more evenly cooked item as a result.

      1. re: HaagenDazs

        Unfortunately, I do not have the roast in my possession, its at my parents' place. I had my dad take a measurement and it look like its 17 inches long. My roasting pan, as it turns out, is only 16.5 inches long. I may have to split into two no matter what! Maybe take a few ribs off one end for the people that cant stand the sight of rare meat, and leave 14 inches for the rest of us? obviously, the smaller piece will cook in a shorter amount of time.

        I do have a probe thermometer, actually I will be using a couple.

        Also, would anyone suggest using convection bake?

        For sure I will have the roast out of the oven at least 2 hours prior.

        1. re: nielubow

          If you're going to cut it, I say cut it truly in half. I wouldn't complicate things by making larger and smaller pieces with different cooking times but that's just me.

          It sounds like you've got the thing under control so you know that the end pieces are going to be more well done anyway. Convection is great for items like this, I think. As with anything cooked by convection, watch that browning!

          1. re: nielubow

            Just did a 15 1/2 lb prime rib over the weekend on Convection roast and it was perfect. If you are using convection, no need to start out high like others suggest....convection will take care of the browning.

            1. re: ammel_99

              Definitely use a temperature probe. Did a 24 pound turkey set at Convection, and it was done in half the time that the turkey packaging called for (non convection oven).

                1. re: itryalot

                  Convection roast at 350 and probe thermometer set to 118 degrees.

              1. re: nielubow

                Unfortunately, I do not have the roast in my possession, its at my parents' place. I had my dad take a measurement and it look like its 17 inches long. My roasting pan, as it turns out, is only 16.5 inches long. I may have to split into two no matter what! Maybe take a few ribs off one end for the people that cant stand the sight of rare meat, and leave 14 inches for the rest of us? obviously, the smaller piece will cook in a shorter amount of time.

                My suggestion is to leave the roast whole and trim an inch or so to make it fit in the pan you have, rather than cutting it into two separate roasts. You can save the trimmed piece or pieces for steaks. There will be some shrinkage, so the roast will tighten up somewhat and fit in the pan better as it cooks.

                My only word of caution is to use a pan with sides in the two inch range and to roast on an elevated rack if possible for better circulation. If you you use a high sided pan the roast can look grayish roasting at a low temperature and if you do not sear or brown at a high temperature

            2. re: sarge

              Whole !! My X-mas rib roast is 13 - 15 most years, aways whole, not ice cold, semi room temp. 300 oven, about 2 1/2 hours most years. let it rest before cutting. Look at your guests eyes when you take that whopper out of the oven.

            3. Check this site:

              Cooking Time for Rare (120°


              (3) Ribs, 7 to 8 lbs. 15 minutes at 450°, Then 1 ¼ to 1 ½ hours at 325°
              (4) Ribs, 9 to 10 lbs. 15 minutes at 450°, Then 1 ½ to 2 hours at 325°
              (5) Ribs, 11 to 13 lbs. 15 minutes at 450°, Then 2 to 2 ½ hours at 325°
              (6) Ribs, 14 to 16 lbs. 15 minutes at 450° Then, 2 ¾ to 3 hours at 325°
              (7) Ribs, 16 to 18 lbs. 15 minutes at 450° Then, 3 to 3 ¾ hours at 325°

              3 Replies
              1. re: grampart

                Please be aware that guidelines like this are VERY broad approximations at best. A thermometer is the only way of ensuring correct temperature, and in my opinion a probe thermometer that constantly measures temperature is the best way to go so you don't overcook it.

                Another essential tip is to allow this to come to room temperature before cooking. Be aware this may take 2-4 hours.

                1. re: grampart

                  I used this chart to cook a 21-pound rib roast (I left it in one piece). Salt/pepper/garlic/onion rub and option (7): 15 minutes at 450 Then, 3-3/4 hour at 325. Internet temp was 120. Rested for at least 20 minutes and was medium-rare.

                2. I say keep it whole. It will make a fabulous presentation. I once cooked a 25 lb. standing rib roast in the Weber kettle. Talk about delicious!!

                  Personally, I think 450 is too high. I used to roast beef for 17 per lb. at 325*/ interior temp 125* for medium rare...15 min per lb for rare.

                  4 Replies
                  1. re: Gio

                    The thought behind high temps (whether at the beginning or the end) is for creating a browned crust, not cooking the meat by any appreciable measure. That's why there's "15 minutes" before the 450 degree instruction. ;-) I think it's a good idea to do at some point (like I said, beginning or end) during the cooking process. I opt for the beginning of cooking so you don't potentially overcook the outside.

                    1. re: HaagenDazs

                      HD: Many thanks for the explanation. Ever since DH had his heart by-pass we stopped red meat per the Dr.'s orders. So we don't do roast beast any more...sadly.

                      I really don't have any earth shattering tips... We used wood chips, a chimney starter, and pretty much it was straight forward grilling by the "Indirect" method. We also used to place the roast, seasoned with Kosher salt & freshly ground black pepper only, on a rack set in the same kind of roasting pan we use in the kitchen oven but that we just use in the Weber. That collected the drippings nicely. If you have a Weber, then you probably have their handy-dandy booklets which give tons of information. Oh and yes, the thermometer is a must.

                    2. re: Gio

                      Any tips on doing one in a kettle?

                      1. re: Gio

                        Wow! 25# on the Weber. Be still my heart. Could you handle a couple more the next time you do that??? Please :)

                      2. I say keep it whole, unless you think yu will have trouble getting it in and out of the oven.

                        1. Now that you've determined you need to split the monster anyway, take advantage of the benefits. Now you will have twice as many end pieces, for those who like the crusty, heavily seasoned, more welldone portions. Definitely invest in a probe thermometer. Realize that even if both pieces are identically sized, they may cook at VERY different rates, depending on shape, structure, position in the pans and oven, and mere chance. Unless you are cooking very long and low (as many prime rib restaurants are able to do) your meat will coast up another 5 degrees or more after being removed from the oven. Resting time is crucial for juices to redistribute through the meat and not come spilling out onto the board. Enjoy -- as long as you pay attention to temperature, a standing rib roast is fairly simple and very delicious. Report back.

                          1 Reply
                          1. re: nosh

                            Well, its over. The 18.55 lb beast has been cooked and eaten! Here's how it happened....I let the roast sit at room temp for about 3 hours. I removed the boned then tied back on for easy removal and carving. Rubbed with 1.5 sticks of butter mixed with a lot of salt and pepper. Only problem here was that I always seem to have a problem with the butter having trouble adhering to the meat. I tried to dry the surface with paper towels hoping to get better sticking but its still difficult (any tips here?). I did the best I could and it seemed to create a nice crust. I dont think you can add too much salt to something like this!

                            Cooking method: Since the roast would not fit in a standard roasting pan, I used a 20-22 inch disposable aluminum pan, doubled up. Turns out it was the just the right size. 425 convection bake for 15 minutes. Then convection bake at 250 until the thermometer read 125 (I went a little higher than normal since my cooking temp was pretty low and did not expect too much carryover cooking). I would have cooked at 225 convection but the oven would not go so low. I used 2 insta-read thermometers about 8 inches apart near the center of the roast. The roast rested for about 40 minutes. Total cooking time was about 3 hours ( I didnt really pay attention to time, but the thermometer).

                            First few cuts came from the end for the babies :-). Then I went right for the center for the rest of us. Nearly the whole cross section of the meat was medium rare to rare with the exception of the outer 1/2 inch. It was a thing of beauty and it tasted great!

                            Thanks everyone for your help and have a pleasant holiday season!

                            BTW - one poster above assumed that I was female, while in fact I am a 30 year old guy. What was it about my original post that may have indicated otherwise:-)?

                          2. I picked up my 16 lber this morning. I am planning to keep it whole (maybe even putting on a cookie sheet). I am going to do the high temp for 15 (love the crunchy crust) and low temp the rest, using a probe thermometer.
                            I am wondering if I too should use my convection and which setting, roast or bake?
                            Should be interesting; I am removing on of the racks from my oven.

                            5 Replies
                            1. re: itryalot

                              Be careful when using the convection settings and know what each one does. Usually when given the choice, the bake setting turns on the bottom element and the roast setting turns on the top element. I don't have a convection, so I don't know specifically (cousin has one that I've used before), but I would venture to guess that for such a long cooked item, the bake setting is most appropriate.

                              1. re: HaagenDazs

                                I am wondering how much quicker the convection setting will cook the roast?

                                1. re: nielubow

                                  It depends on your oven temp and it depends on if your convection fan has a heating element inside it as well (probably does). Usually with convection you cook for about 25% less time, but again, it all depends on what your target oven temperature is. There are some variables that you need to figure out here.

                                  If it were me, I would aim to roast this at about 275-300 degrees in a standard oven.

                                  By using convection, if you keep that same temperature, the meat might behave as if the oven temperature is actually at 325 due to the forced air (I'm totally guessing here by the way). That's fine, just expect it to be done 25% sooner, on average.

                                  Conversely, you could also reduce the oven temperature by say, 25 degrees to 250, but then you could expect the beef to be done about the same time as a standard (non-convection) oven. So there are some decisions you can make there, and you can follow the chart that grampart added (above) to give you a very rough scale on how long the roast will take.

                                  I'll echo the ammel 99 post above that if you're using convection you won't need to start the roast at a high temp, the crust will be formed even more efficiently by using the convection setting.

                                  1. re: HaagenDazs

                                    Definitely go with the reduced temperature. The cooler your oven, the more evenly the meat will cook. And if you decide you need more crust at the end, just crank up the heat.

                              2. re: itryalot

                                Convection roast which will also give you the perfect crunchy crust without the high temp start. I set my probe temp to 118 and after resting for an hour meat was perfect med rare! I took tip of dry aging in the fridge for 3 days (from Alton Brown recipe) and it was really tender.

                              3. A couple of years ago one of my vendors gave me a 22# standing rib roast - USDA Prime, no less - as a Christmas gift. We always spend Xmas at my sister's house, so I packed up the rib roast in my suit case and flew with it (and paid an excess weight fee too).

                                We were face with the same dilemma of whether to cut the thing into two pieces or not. Since there were going to be a number of seniors and some others who wouldn't eat meat with any red in it, we elected to cut the thing in two so that one piece could be roasted rare and the other more well done. My sister has a fabulous kitchen with great appliances, including double convection ovens. Turns out we made the right decision, but for the wrong reasons.

                                Christmas day dawned cold, overcast and somewhat stormy and got even stormier as the day wore on. A couple hours after the roasts went into the oven the power went out. After confirming that the power outage would be rather long and much debate (at least 30-45 minutes worth) about alternate dining options for 18 people with no reservations and the state of the rest of the dinner preparations, we decided to stay put and salvage what we could of the meal. Of course, the only thing I could think of was how unfortunate it was that 22 lbs. of USDA Prime rib roast was ruined. (I was so obsessed with cooking this roast "right" I took the internal temperature as soon as the power went out and wouldn't let anyone open the oven door.)

                                Thank god for gas ranges and grills, we got the rest of the meal done while my BIL carved the roasts by candlelight. In semi-darkness and late afternoon twilight, he said it all looked like it was well done :-(. We ate, we drank good wine, we had a good time and laughed a lot about being left in the dark. Several hours passed and we decided we might as well attempt cleaning up by flashlight. As if on cue, the lights came back on. It was then that we discovered both roasts had been cooked perfectly. The smaller roast was originally going to have been rare, it came out medium well. The larger roast was originally going to have been medium well, it came out medium rare.

                                The moral of the story? Trust that whatever decision you make regarding your roast will be the right one. Don't sweat the small stuff...one roast or two? conventional vs.convection? The holiday dinner is not about whether or not the prime rib is "perfect", it's about the connection and affection with those at the table :-)

                                P.S. Do use a thermometer to register the internal temperature.

                                2 Replies
                                1. re: DiningDiva

                                  Great story and lesson. Did you know that you inadvertantly followed a roasting method for standing rib roasts that i first heard about on a radio cooking show and that you can read about on www.melindalee.com -- which calls for starting the roast in a hot oven for a relatively short period of time and then turning the oven off. An essential element, but one that is extremely hard to resist, is that you cannot, must not open the door.

                                  1. re: DiningDiva

                                    After my comment was deleted, I'll simply put in my own moral of the story: This very expensive cut of beef so the point I would like to stress is that you need to use a probe thermometer. There should be no guessing when it comes to cooking a rib roast no matter how important the family get-together is.

                                  2. IMHO, a whole rib roast is a thing of beauty; cutting it in half would be a shame. If you have to do it, you have to do it, but if there's any way to avoid it...

                                    The roast is somewhat malleable and is going to shrink a little as it cooks, so I wouldn't worry too much about fractions of an inch when it comes to the size of your pan. The size of the oven, on the other hand, is significant; you need enough room on each end for air to circulate. The convection feature will be especially helpful in this regard.

                                    For those who prefer their meat more well-done, have a pan of beef broth standing by on the simmer. A few seconds in a hot bath will bring slices to the desired doneness.

                                    1. Out of curiosity, how long would a 16lber take? I am trying to time it backwards. Med doneness in the center and med/well near the outside, or a nice light pink through.

                                      1 Reply
                                      1. re: itryalot

                                        There are wayyyyy too many variables to cook by time. Internal temperature of the meat, precise temperature of your oven, even the way the fat is marbled. But at 325F, you can figure on 3.5 to 4 hours in the oven, plus resting time after that. The resting time gives you some wiggle room as far as getting it on the table when everything else is ready. You can let the roast sit on the counter, tented in foil, for an hour or more.