HEAT oil in large nonstick skillet on medium-high heat. Add chicken; cook 2 min. on each side or until browned on both sides. Remove from skillet; set aside.
ADD onions, garlic and 1 Tbsp. dressing to skillet; cook and stir 4 min. or until onions are tender. Stir in remaining dressing, tomatoes and olives; top with chicken. Simmer on medium-low heat 25 min. or until chicken is done (170ºF) and mixture is heated through, stirring occasionally.
STIR in basil; top with Parmesan.