In a large bowl, combine cooked pasta, 3 cups mozzarella cheese, cottage cheese, eggs, Parmesan cheese and parsley. Transfer to a greased shallow 3 quart baking dish (I used a deep 9x13) Top pasta mixture with beef and onion mixture, then pasta sauce.

Cover casserole and bake for 45 minutes. Uncover and sprinkle with remaining mozzarella cheese. Bake, uncovered, for an additional 15 minutes longer until cheese is melted. Let stand 10 minutes before serving.