MICROWAVE chocolate in microwaveable bowl on MEDIUM 2 min. or until chocolate is almost melted, stirring after 1 min. Stir until chocolate is completely melted.
STIR in 3/4 cup each of the grahams and marshmallows. Spread onto waxed paper-covered baking sheet. Decorate with remaining grahams and marshmallows.
REFRIGERATE 1 hour or until firm. Break into 60 pieces.