Saute onion in olive oil, medium heat, for 5 minutes. Add sliced squash and cook for another 5 to 10 minutes depending on how soft you like it.
Mix crackers, cheese, egg, milk, butter and seasonings together in large bowl. Stir in the cooked squash.
Spray dish (I used a glass casserole) with cooking spray and dump the squash mixture in, spreading it evenly.
Bake at 400 degrees until nicely browned, about 25 minutes.
You can add other spices or seasoning - parsley flakes, oregano, etc. to add your favorite flavor. You can't mess it up - a pretty basic recipe. Less or more cheese, more buttered cracker crumbs on the top, etc.