Preheat oven to 350 degrees. Spray bottom of 12-inch round pizza pan with cooking spray. Set aside.
Put 2/3 of cookies in food processer. Coarsely crush. Cut remaining cookies into small chunks.
Prepare brownie mix according to package. Stir in crushed cookies.
Pour batter into prepared pan.
Bake 18 to 20 minutes or until edges have firmed.
Sprinkle with marshmallows. Bake another 1-2 minutes until marshmallows are soft and puffy. Remove from oven and immediately sprinkle with cookie chunks and caramel M&M's. Serve warm.