Preheat oven to 400°. In a small skillet, heat oil over medium heat. Add onion and garlic; cook until onion is tender and golden brown, 5-9 minutes. Cool slightly., In a large bowl, combine bread crumbs, eggs, cheese, parsley, water, basil, Worcestershire sauce, salt, pepper and onion mixture. Add ground meats; mix lightly but thoroughly. Shape into 1-in. balls. Place on greased racks in shallow baking pans. Bake until browned, 20-25 minutes., Transfer meatballs to a 4- or 5-qt. slow cooker. Pour spaghetti sauce over top. Cook, covered, on low until meatballs are cooked through, 3-4 hours. If desired, serve with minced parsley.