Heat oil in large skillet. Add chicken pieces, brown and set aside. Add onion,green pepper and garlic; Cook until onion is tender. Force Italian plum tomatoes through a strainer. Add tomato liquid,parsley, oregano, thyme, salt and pepper to skillet. Cook over low heat for 15 minutes; stir occasionally. Add chicken; cover and cook over low heat 45 minutes. Stir occasionally. Add mushrooms. Cook uncovered 15 minutes or until sauce is desired consistency.