1 1/4 lbs. ground beef
1 onion, finely chopped
1 (32 oz.) jar spaghetti sauce
1/2 c. grated Parmesan cheese
7 pieces manicotti noodles
12 oz. shredded Mozzarella cheese

Brown meat and onion; drain. Stir in a little over half the sauce and half the Parmesan cheese. Put in part of the Mozzarella and stir to melt. Stuff each piece of manicotti with meat mixture and place in baking dish. Spoon remaining meat mixture, sauce, and cheeses over manicotti. Bake at 350 degrees for 30 minutes.