1 lb. extra lean hamburger
2 tbsp. dry bread crumbs
1 egg
1 c. grated Parmesan cheese
2 tbsp. olive or vegetable oil
1 lg. sweet onion, thinly sliced
1/4 tsp. salt
1/8 tsp. pepper
1/8 tsp. dried oregano leaves
1 (8 oz.) can tomato sauce
1 c. Mozzarella cheese, shredded
4 thick slices Italian bread, toasted and buttered

In large bowl, combine beef, crumbs, egg, and 1/3 cup Parmesan cheese. Divide into 4 parts. Shape into patties. Heat oil in heavy skillet; add patties. Brown over high heat 1 minute on each side. Place into a shallow baking dish.

Add onions to drippings in skillet; cook on low heat 5 minutes. Add salt, pepper, oregano, and sauce; simmer 5 minutes. Sprinkle 1/3 cup Parmesan cheese over meat patties; top with sauce mixture. Sprinkle with remaining cheese.

Bake at 375 degrees for 30-35 minutes until sauce is bubbly and meat is cooked. Serve on top of bread.