MKE TO MSP CORRIDOR I-90 & I-94
The only place I can think of is the Norske Nook in Osseo. There you will find the best pie in the state. The rest of the menu is typical comfort food--hot sandwiches swimming in homemade gravy, next to a pile of mashed potatoes. Nothing terribly exciting or innovative, but, far better than any of the chain fast food junk off the rest interstate.
Norske Nook Kaffe Hus
13807 7th St, Osseo, WI 54758
As MilwaukeeChow says, the Norske Nook is worth a stop for pie.
There are several worthy stops in the Dells. My personal favorite is the Cheese Factory for lunch. Essen Haus is also good for German food.
A bit north of the Dells, at Camp Douglas, is German Haus. It's right off the highway and does decent wienerschnitzel and other German standards.
I have driven this stretch a hundred times and have yet to find a Holy Grail, a place right off the interstate that has chow so good it would be a destination in itself. That said, here are some places I have at least enjoyed, roughly in order of their location on a trip from MKE to MSP:
Teddywedgers Pasties in Madison at the corner of State Street right accross from the capitol. This is my favorite chowish destination on this list, but being downtown it is a 10-15 minute drive off the interstate. This is a tiny little takeout place, though, and there are many other of good restaurants along State Street. so if you are going to the center of Madison anyway there are many choices.
Pine Cone (I have eaten at the Hwy 51 exit just north of Madison, but there is also one at the Johnson Creek exit just a half hour west of MKE).
Martha's Lyndo Inn Cafe, Lyndon Station (only a half mile off Interstate)
At the Mauston exit we enjoyed an Italian/Greek restaurant on the strip of restaurants on 82. Its on your left as you drive toward downtown Mauston on 82 (south side of 82) just past the Culver's only a half mile off the interstate. Some name like Roman Palace. Can't find it in web searches. Only CJ's Italian comes up and thats not the place. Wonderful rolls.
Monk's Bar in the Dells-- burgers!
Target Bluff German Haus at the Camp Douglas exit (with the rock that looks like a castle)-- can't really vouch for the food--its been too many years and I can't remember, but the place is a hoot, so I'd be willing to try it again.
The Bog (Warren Exit, a few miles north of Tomah, so just past your halfway point).
Northfield exit (exit 98): We enjoyed Jackies Inn Bar & Grill--Just a little small town bar & grill, but decent hamburgers and delicious greasy homemade potato chips. We only went there because DeeDee's Diner next door was closed (it being suppertime and the diner open breakfast-lunch only). Still haven't tried DeeDees
I have become so disillusioned with Norske Nook food that if I was stopping for a meal in Osseo, I would rather try one of the Bar & Grill places on Main Street (and then perhaps get pie at the Nook).
And of course there is a Culvers at almost every other exit, which is good food for what they do. But its a chain, so where's the fun in that?
Pine Cone Restaurant
6162 US Highway 51, De Forest, WI 53532
Myles Teddywedgers Cornish
101 State St, Madison, WI 53703
Martha's Lyndo Inn Cafe
111 E Flint St, Lyndon Station, WI 53944
220 Broadway, Wisconsin Dells, WI 53965
3514 Blarney Rd, Warrens, WI 54666
Target Bluff German Haus
1216 State Road 208, Camp Douglas, WI