Preheat oven to 350F
Grease 9x13 pan with cooking spray.
Mix together the graham crackers and butter.
Sprinkle into the baking dish and press firmly on bottom and up the sides of the pan.
Bake 8 minutes.
Remove from oven and sprinkle chocolate chips on top, followed by marshmallows.
Bake for 20 minutes, until marshmallows turn brown.
Let cool then place in fridge.
Cut and serve
