Squash Casserole

This is the best squash casserole I have ever eaten!

6 medium sized yellow squash, sliced
1 large onion, chopped
2 stalks celery, chopped
1 medium bell pepper, chopped
2 slices white bread, cubed
salt and pepper to taste
1 stick oleo
1 egg
1 c. milk
1 c. grated cheese
cracker crumbs

Cook squash, onion, celery and bell pepper until tender. Drain. Add oleo and bread. Stir. Cover and set aside. Mix egg, milk, salt and pepper if needed, and stir into squash mixture. Add cheese, stir and pour into greased casserole dish. Top with crushed Ritz cracker crumbs and melted butter mixture. Bake at 350-400 degrees until top browned and casserole is bubbling (35-45 minutes).