In a large bowl, combine the brown sugar, butter, eggs and vanilla just until blended.
Combine the flour, baking powder and salt; add to brown sugar mixture.
Stir in chocolate chips.
Spread into a greased 13-in. x 9-in. baking pan.
Bake at 350° for 18-20 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack.
Cut into bars.