Squash Casserole PREHEAT OVEN TO 350 DEGREES. 2 1/2 pounds of either zuchini or yellow squash (or, to make it prettier, use a combination of the two) Sice the squash. Let it sit for a few minutes, then pat it very dry. Then combine the ingredients below. Add fresh ground pepper and a small amount of kosher salt. 1 cup mayo 1 egg, slightly beaten 1 cup parmesan cheese 1/2 cup finely chopped onion 1/2 stick of butter, melted Add the squash to the wet mixture. Spread into a well-greased 9 x 13 pan. Top with your favorite casserole topping (crushed Ritz crackers with a little butter, french friend onion rings, etc.) Bake for 50 minutes at 350 degrees, or until the top is a beautiful brown color. Perfect for summer time when you have squash in abundance, but it's a great dish anytime that goes well with many things. Posted by Mary Beth Guard.