1Heat oven to 350°F (325°F for dark or nonstick pan). Spray 15x10x1-inch pan with baking spray with flour.
2In large bowl, beat cake mix, softened butter and eggs with electric mixer on medium speed about 1 minute or until well blended. Spread evenly in pan.
3Bake 19 to 24 minutes or until top is evenly golden brown and toothpick inserted in center comes out clean. Cool completely, about 1 hour.
4Spread frosting evenly over cooled bars. Top with berries up to 2 hours before serving. For 48 bars, cut into 8 rows by 6 rows. Store covered in refrigerator.