lexigman, you don't mention how many people you're looking to have catered for & any particular cuisine, but a lot of Chicago restaurants are good options depending on the size of your group & can be very cost effective.
I attended a wedding a few years ago at the South Shore Cultural Center for which Furama on Broadway did the catering for about 150 people, they did a very nice semi-traditional Chinese banquet & supplied the wait staff too (the couple was Southside Irish catholic & LA Chinese-America, so I think there were some concessions to making sure there were enough dishes everyone was comfortable with). It was one of the most fun wedding dinners I've been to plus the food was very good.
Noon-o-Kebab is a good option & so is Salaam (& Nazareth & Jaffar Sweets are happy to do dessert tables for events).
If Indian isn't too exotic for your guests, India House has a huge catering group that supplies a lot of local weddings & they are used to dealing with large numbers.
I've been to a bunch of events that used Wolfgang Puck Catering - its good, but I suspect its pretty pricey.