HEAT oil in large nonstick skillet on medium-high heat. Add mushrooms and onions; cook 5 min., stirring occasionally. Stir in tomatoes, dressing and tomato paste.
ADD chicken; cover. Simmer on medium-low heat 12 min. or until chicken is done (165°F).
TOP with cheese and bacon; simmer, uncovered, 5 min. or until cheese is melted.