1. Heat oven to 375°F.
2. Prepare shells as directed on package; drain.
3. While the shells are cooking, brown meat with peppers and onions in large skillet; drain. Stir in pizza sauce.
4. Spoon cooked shells into 8-inch square baking dish; top with meat mixture and mozzarella. Cover.
5. Bake for 20 minutes or until heated through. Serve immediately.