Preheat oven to 350. Saute onion in butter for 5 minutes. Remove from pan and mix all ingredients together. Pour into buttered casserole dish and top with cracker crumbs. Bake for 25 to 30 minutes.
Variation: For a different taste to this casserole, layer slices of cooked red potatoes in the bottom of the casserole dish, followed by squash mixture, repeat layers. Top with about 1 cup Ritz crumbs tossed with melted butter.