Preheat oven to 350 degrees F (175 degrees C). Prepare brownie mix according to package directions. Spread into a greased 9x13 inch pan.
In a medium bowl, break graham crackers into 1 inch pieces and toss with miniature marshmallows and milk chocolate. Set s'more mixture aside.
Bake brownies for 15 minutes in the preheated oven. Remove, and sprinkle the s'more goodies evenly over the top. Bake for an additional 15 to 20 minutes, or until a toothpick inserted in the center comes out clean. Allow brownies to cool before cutting into squares.