Preheat oven to 350°. In a large bowl, cream butter, peanut butter and sugars. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla. Combine flour, baking powder and salt; gradually add to creamed mixture. Stir in chocolate chips.
Spread into a greased 13x9-in. baking pan. Bake 45-50 minutes or until a toothpick inserted in the center comes out clean. Cool on a wire rack. Cut into bars.