Preheat oven to 350 degrees F. Spray a 9x13-inch baking pan lightly with cooking spray; set aside. In a large mixing bowl, stir together all ingredients, except powdered sugar, until well combined. Spread batter evenly into prepared pan.
Bake in preheated oven for 24 to 26 minutes or until a toothpick inserted in brownies two inches from the edge of the pan comes out almost clean. Cool completely on a wire rack before cutting. Before serving, dust brownies with powdered sugar.