Meanwhile, cook chicken in large nonstick skillet on medium heat 3 to 4 min. on each side or until golden brown. Transfer to plate; cover to keep warm. Add dressing, mushrooms and peppers to skillet; cook and stir 6 min. Add tomatoes; simmer 8 min. Return chicken to skillet; spoon sauce over chicken. Simmer 3 min. or until chicken is done (165ºF).