not a marinade but more of a wet rub:
3-4 cloves garlic minced with
2 tsp kosher salt
Add 2-3 T minced fresh rosemary leaves
1 T fresh ground peppercorns
1 1/2 tsp allspice
3-4 T olive oil
Mix and rub onto lamb as it sits on the counter to come to room temp before grilling.
adapted form a Julia Child recipe for pork loin.
These days for me it's a marinade with turkish spices featured in both Sortun's Spice and Wolfert's Eastern Med cookbooks.
The marinade for 3lb of butterflied leg is 2tbs aleppo pepper, 2tbs baharat (Kalustyans), 1/2 tbs dried crushed mint, 1/2tbs dried chrushed oregano, 1/4 cup of good tomato paste, 2tbs of red pepper paste (i usually used piquillo peppers minced to a paste), 1tbs of minced garlic. Spread over the meat, then cover with 1/4 good canola oil, and leave aside in cool place up to 4 hours.
We usually grill this for 3mins on each side to char a bit, and then cover and do indirect grilling for 10-15mins more.
I marinate mine, pounded to even thickness, in a bottle of decent red wine, seasoned with salt, pepper, olive oil, a few cloves garlic, and sliced onion, for 8 hours or so. A recipe along these lines appeared in Gourmet in the 1980s and I have made my grilled lamb, cooked medium rare, this way ever since. A little fresh thyme is a nice addition.
marinate in garlic, lemon juice and oregano overnight.
While on the grill, continue to base with the marinate. (I use a long sprig of rosemary to apply the marinade, like a brush.. I find this gives just the right amount of rosemary flavour... if you actually marinade it in rosemary, I find the taste too strong and can overpower the lamb)
Serve with a fetta and spinach salad
I'm a sucker for a traditional rosemary garlic marinade for leg of lamb.
Chop up a good handful of fresh rosemary. Mash about 6-10 cloves of garlic to a paste. Add 1 or 2 TB salt, 1 TB pepper, and stir around 1/4 cup olive oil to the mix. Spread it all over the leg, let it sit overnight and then grill the next day. Not original, but really, really good.