Heat oven to 350°F. In medium bowl, mix powdered sugar, peanut butter and vanilla until well blended.
Cut cookie dough in half. In ungreased 8- or 9-inch square pan, break up half of dough. With floured fingers, press dough evenly in bottom of pan. Press peanut butter mixture evenly over dough. Crumble and sprinkle remaining half of cookie dough over peanut butter mixture. Carefully spread as evenly as possible.
Bake 30 to 35 minutes or until golden brown and firm to the touch. Cool 30 minutes. Refrigerate 1 hour or until chilled. For bars, cut into 4 rows by 3 rows. Serve chilled or at room temperature.