Milwaukee has a number of good restaurants in the area. And if you are doing a "segments & miles" MR you can easily do a quick segment from ORD-MKE-ORD and pick up a couple of quick segments. Some MKE restaurants (of the 136 United IDINE restaurants in the MKE metro area) include:

Fine Dining: Aqua (Downtown - Hot Deal offering double miles), Gasthaus (far West Suburban German restaurant), Koerpers (Well known near-downtown steak house), Mo's A Place for Steaks (downtown), Pleasant Valley Inn (West), Third Street Pier (downtown)
Pizza:Balistreri's Italian Restaurant (West Side - Sunday to Thursday only), Zaffiro's
Fast Food: Omega Custard (Hwy 100 and Layton), Bella's Fat Cat (Multiple Locations)
Breakfast: Johnny V's Classic Cafe (West Side working man's breakfast), Pegasus (West Side working man's breakfast)
Pub Fare: County Clare (near downtown), John Hawks Pub (downtown), Mo's Irish Pub (downtown),
Mexican: La Perla, Senor Luna (multiple locations - my wife loves the seafood enchiladas)
Unique Milwaukee Experience: Edelweiss Cruiselines

Although there are many others, this offers some guidelines.