HEAT oven to 375ºF.
POUR dressing over chicken in shallow dish; turn to evenly coat both sides of each breast. Refrigerate 30 min. to marinate.
MIX cooking creme and milk in large bowl until blended. Add potatoes, broccoli and 1/2 cup shredded cheese; mix lightly. Spoon into 13x9-inch baking dish sprayed with cooking spray.
REMOVE chicken from marinade; discard marinade. Place chicken over vegetable mixture; sprinkle with pepper. Cover.
BAKE 1 hour or until chicken is done (165ºF), uncovering and sprinkling with remaining shredded cheese after 45 min.