Pizza Casserole

1-12 Oz. Package whole grain macaroni
1/4 Cup diced onion
2 Tablespoons margarine
2 Pounds  ground beef
2 Cups small curd cottage cheese
1/4 Cup grated Parmesan cheese
1-12 oz.  can pizza sauce
1  ( 8 oz.) fresh mushrooms,
1 Teaspoon oregano
1 1/2 Teaspoon salt
1 Cup sour light cream
Cook macaroni, rinse and drain.  Sauté onion in margarine until transparent.  Add beef and brown. Drain excess fat.  Combine meat with remaining ingredients and mix with macaroni.  Pour into casserole.  Sprinkle with additional Parmesan cheese.  Bake at 350 degree for 45 to 60 minutes.  Serves 8.