In A Bowl, Mix The Ground Beef, Bread Crumbs, Parsley, Garlic, Onion, And Egg. Shape The Mixture Into 16 Meatballs. In A Slow Cooker, Mix The Spaghetti Sauce, Crushed Tomatoes, And Tomato Puree. Place The Meatballs Into The Sauce Mixture. Cook On Low For 6 To 8 Hours.