Set oven to 350 degrees F for metal or glass pan. For dark coated pan, set oven to 325 degrees F. Coat bottom of pan with no-stick cooking spray.
Stir brownie mix, water, oil and egg in bowl until blended, about 50 strokes. Spread into pan.
For 8x8-inch pan, bake for 29-32 minutes.
For 9x9-inch pan, bake for 26-29 minutes.
Cut and serve when completely cooled. Store loosely covered.