Have you checked out the "supper club" menus of various restaurants? I believe these restaurants offer them where you can feed a good amount of people resonably and these locations may be able to accomodate your party:
Wildfire - Lincolnshire or Downtown
www.wildfirerestaurant.com
Maggiano's - Skokie
www.maggianos.com
The Palm - Northbrook
www.thepalm.com
For something other than chains, there is a plethora out there....depends if you're looking for a specific cuisine.
For a bridal party, there is also the Chocolate Buffet at the Peninsula Hotel's "The Lobby" restaurant downtown (assuming the ladies love chocolate)
http://chicago.peninsula.com