Place chicken in an 11-in. x 7-in. baking dish coated with cooking spray.
In a small bowl, combine the salad dressing, avocado and 2 tablespoons cheese; spoon over chicken. Bake, uncovered, at 375° for 30-35 minutes or until a meat thermometer reads 170°. Sprinkle with remaining cheese. Yield: 4 servings.