Heat oven to 350°F. Grease 13x9x2-inch baking pan.
Beat butter and peanut butter in large bowl. Add sugar and brown sugar; beat well. Add eggs, one at a time, beating well after each addition. Blend in vanilla.
Stir together flour, baking powder and salt; mix into peanut butter mixture, blending well. Stir in peanut butter chips. Spread half of batter in prepared pan; spoon syrup over top. Carefully top with remaining batter; swirl with a knife for marbled effect.
Bake 35 to 40 minutes or until lightly browned. Cool completely in pan on wire rack. Cut and Enjoy!