Heat oven to 350°F. Grease 13x9-inch pan. Prepare brownies as directed on package using oil, water and eggs. Spread batter evenly in greased pan. Press peanut butter cups about halfway into batter, forming 6 lengthwise rows and 5 crosswise rows.
Bake at 350°F. for 30 to 35 minutes. Cool 1 1/2 hours or until completely cooled. Cut into bars with 1 peanut butter cup in center of each.