byo Catering

Here are a few options I found. Wasn't sure what your budget is for a venue or what style of venue you were looking for. I was able to find a lot of venues that allow outside catering, but there are a limited number that can accommodate 250 people.

https://moonlightstudioschicago.com/

https://www.dankhaus.com/

https://rialtosquare.com/ (caterers not on the preferred list must be approved)

https://www.stanmansion.com/ (website says they have a preferred list, but based on reviews I read you can use your own)