Wash and cut up squash. Steam until just tender, then drain and set aside. Saute onion in butter or oil until clear and tender. Add cracker crumbs to onion and brown, stirring constantly. Stir in chopped parsley and peppers. Mash the squash slightly. Add to crumb mixture. Season with salt and pepper to taste. Turn into a flat casserole or baking dish. Sprinkle with grated cheese and additional crumbs. Bake at 350 degrees F for 30 minutes.