In a large bowl combine ground beef with italian sausage and mix well. Add beaten egg, onion, salt, pepper and seasoned bread crumbs. Mix together and shape into meatballs - about 1 1/2" to 1 3/4" round.
Place in a lightly greased 9" x 13" baking pan or casserole dish; Bake, uncovered, at 375º for 30 to 35 minutes. Drain off fat before serving.