In a 3-1/2- to 6-quart slow cooker, combine cabbage wedges, onion, and mushrooms. Sprinkle tapioca over vegetables. Place chicken pieces on vegetables. Pour spaghetti sauce over chicken.
Cover and cook on low-heat setting for 6 to 7 hours or on high-heat setting for 3 to 3-1/2 hours. Transfer to a serving platter. Sprinkle with Parmesan cheese. If desired, serve with hot cooked pasta. Makes 4 to 6 servings.
