Italian Stuffed Meat Loaf

Meat Loaf
1 pound lean ground beef
1 cup oats
1 (15 1/2 ounce) jar spaghetti sauce, divided
1/2 cup chopped onion
1/3 cup grated Parmesan cheese
1 egg, slightly beaten
1 tablespoon Worcestershire sauce
1 teaspoon pepper

Filling
1/3 cup of any one or all of the following:
    sliced mushrooms, sliced ripe olives, shredded
    mozzarella cheese, shredded zucchini

Topping
1/2 cup shredded mozzarella cheese
Ripe olives, sliced

Preheat oven to 350 degrees F. Grease an 8-inch square baking pan.

For meat loaf, combine ground beef, oats, 1/2 cup spaghetti sauce, onion, Parmesan cheese, egg, Worcestershire sauce and pepper; mix well. Separate mixture into two equal parts. Shape each into a patty about 7 inches in diameter. Place filling on one patty to within 1/2 inch of edge. Place in prepared pan. Bake 45 to 50 minutes or until meat is done. Top loaf with remaining spaghetti sauce and mozzarella cheese. Garnish with olives.