Heat remaining 1 tablespoon olive oil in same skillet and cook mushrooms, peppers and onion, stirring occasionally, 5 minutes or until tender and golden. Stir in sauce and oregano. Bring to a boil over high heat. Return chicken to skillet, reduce heat to low and simmer covered, stirring occasionally, 10 minutes or until chicken is thoroughly cooked. Serve over hot spaghetti and garnish with cilantro.