PREHEAT oven to 350°F. Grease a 15x10-inch jelly-roll pan.
COMBINE flour, baking powder and salt in medium bowl. Beat butter, granulated sugar, brown sugar and vanilla extract in large mixing bowl until creamy. Beat in bananas and egg. Gradually beat in flour mixture; stir in morsels. Spread into prepared jelly-roll pan.
BAKE for 20 to 30 minutes or until wooden pick inserted in center comes out clean. Cool completely in pan on wire rack. Sprinkle with powdered sugar.