1Heat oven to 350°F. Grease bottom only of 13x9-inch pan with cooking spray or butter.
2In large bowl, beat butter, brown sugar, vanilla and eggs with electric mixer on medium-high speed until blended. On low speed, beat in flour, baking powder and salt until soft dough forms. Spread in pan. Sprinkle chocolate chips evenly over top.
3Bake 25 to 30 minutes or until edges are golden brown. Cool completely, about 3 hours. Cut into 6 rows by 4 rows.