Heat oven to 350°. Grease bottom only of 13x9 pan with shortening or spray bottom with cooking spray. Stir brownie mix, water, oil, and eggsin large bowl until well blended. Spread in pan. Sprinkle cookies over batter.
Bake 28 to 30 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean. Cool completely.
Stir together powdered sugar and milk in small bown until smooth and thin enough to drizzle. Drizzle over brownies. Store, covered, at room temperature.
*Servings and yield depends on how big you cut your brownies*.