I seem to remember us having an open house. But as we were a newly colonized chapter (I was one of the first four alums to graduate, all 4 were the same graduation date.) we didn't have a big turnout.
We always have some kind of gathering at our house for alums before tailgating and the game. In the past, it's usually been a BBQ, but this year the game was earlier so we had breakfast with bagels and donuts, etc.