Heat gas or charcoal grill. In small bowl, mix cheese, mayonnaise and dressing; set aside. Spray or brush frozen chicken breasts with cooking spray or oil.
When grill is heated, place chicken on gas grill over medium heat or on charcoal grill over medium coals. Cover grill; cook 10 to 12 minutes, turning once, until juice of chicken is clear when thickest part is cut (170°F).
Spoon and spread 2 tablespoons cheese mixture over entire top of each chicken breast; cook covered 3 minutes longer or until topping is light golden brown and slightly puffy. Sprinkle with chives before serving.