Cut stem end off peppers and remove seeds, wash peppers and drain.
Mix the Italian sausage, seasoned bread crumbs and Parmesan cheese. Stuff mixture into peppers. Place in shallow baking dish. Put enough water to cover bottom. Cover with foil and bake at 400 degrees for 45 minutes.
Gently remove peppers and place in clean baking dish. Pour spaghetti sauce over top.
Return to oven for 10 minutes. Sprinkle top with Mozzarella and leave in oven until cheese is melted. Can be served hot or room temp.