Preheat oven to 350°F. In a large bowl combine mozzarella, Swiss, pepperoni and olives. Mix until lumpy. Add ranch dressing until desired consistency is achieved.
Lay 3 breast pieces out flat and pound the middle of them until you have a pocket. Spoon as much filling into the pocket as desired. Lay the other 3 pieces of chicken over top and pin together with toothpicks. Add one spoonful of filling to tops.