Preheat oven to 375 degrees F.
Mix premade cookie dough with 1 cup of marshmallows.
Line a 13"x18" sheet pan with parchment paper, spraying the parchment with non-stick cooking spray. Layout graham crackers on baking sheet leaving no gaps between them.
Place small scoops of cookie dough on the graham crackers, using an ice cream scoop and spread dough out a little by flattening with back side of scoop or spoon.
Bake for 5 minutes without disturbing.
Press Hershey pieces, 1/3 cup marshmallows. and 1/3 cup broken graham crackers on top.
Bake for 5-7 more minutes.
Cool cookie bars in pan.
Cut cookies into bars or squares.
Store at room temperature in a sealed container.
Makes approx. 30 bars.