There is little fresh they can offer to a crowd of 100K, which is the audience at Oshkosh. Hot dogs, hamburgers, fries, stuff like that. Not high quality from a nutrition standpoint, but quick to make, fried to kill off most of the germs, and a selection so most anyone who is hungry can find something they will eat.
If you're willing to wait in line or eat at off-times, Subway is an on-field choice. Beyond that, you're gonna have to go off grounds or bring your own food to find much that isn't fried.
Personally, I find ways to work around the limitations of the food offered at show center. I visit SOS, the Sleepy Hollow restaurant/bar, a couple of private events in camp Scholar, and make a run to the grocery store. It works for me, but I don't depend on the on-grounds food alternatives.