Combine mushrooms, celery, carrot, onions, sweet pepper, and garlic in a 5- or 6-quart slow cooker. Place chicken on vegetables. Combine broth, wine, tapioca, sugar, oregano, bay leaves, salt, and pepper; pour over chicken.
Cover; cook on low-heat setting for 6 to 7 hours or on high-heat setting for 3 to 3-1/2 hours.
Remove chicken; cover to keep warm. Remove and discard bay leaves. If using low-heat setting, turn to high-heat setting. Stir in undrained tomatoes and the tomato paste. Cover and cook for 15 minutes more. Serve vegetable mixture over chicken and cooked pasta. Makes 6 servings.