The Atrium Center is a new venue in Lansing that possibly could hold that many people. They allow outside caterers/food.
We had both our ceremony and reception at the MSU Horticulture Gardens (on campus). We were able to bring our own food- although the observatory would not fit 400. Depending on the month of your wedding you could check on the larger tented area they have available, possibly called the arboretum?
Click on each tool to see a sample.