Heat gas or charcoal grill. Spray pizza pan or cookie sheet with cooking spray. Remove cookie dough from package; press into disk shape. On pizza pan, roll dough into round about 1/4 inch thick.
Place pan on grill over medium heat. Cover grill; cook 15 to 20 minutes or until cookie is light golden brown. Remove from grill.
Sprinkle graham cracker pieces evenly over cookie; top with chocolate bar pieces and marshmallows. Return to grill; cook about 2 minutes longer or until marshmallows are golden brown.
Cut into wedges. Serve warm.