Combine cooked ground beef and your favorite jarred spaghetti sauce. Pour half of the sauce into the bottom of a greased 9x13 inch baking dish.
In a bowl combine: 3/4 cup mozzarella cheese, cottage cheese, Parmesan cheese, parsley, eggs, and onion.
Gently spoon filling into each manicotti shell and place on top of sauce in baking dish.
Pour remaining meat sauce over the top of the stuffed manicotti shells and top with remaining 3/4 cup of mozzarella cheese.
Bake at 350 degrees F for 35-45 minutes until cheese is melted and sauce is bubbling.