Summer Squash Casserole #2

Another version of the summer squash casserole I tried earlier. This is from Mama Dip's Kitchen.

1.5 pounds yellow and green summer squash, sliced
1/4 cup chopped onion
1/2 stick butter
3 eggs, beaten
1 cup milk
1/2 cup grated Parmesan

Simmer the squash and onion until soft (10 minutes or so) then drain. Cut the butter up and mix it with the squash, then add the milk and Parmesan and stir, then stir in the beaten eggs.

Pour this into a casserole dish and bake at 350 for 40 minutes. I was making the Lemon-Garlic Chicken Thighs at the same time so I baked the squash at 400 and it was fine.