Stir together flour, baking powder, baking soda and salt. In large bowl with mixer at medium speed beat margarine and peanut butter until smooth. Beat in sugars until blended. Beat in eggs and vanilla. Add flour mixture and beat well. If necessary, chill dough. Shape into 1 inch balls. Place on ungreased cookie sheet 2 inches apart. Flatten with floured fork, making crisscross pattern. Bake in 350~ oven for 12 minutes or until lightly browned. Cool on wire rack. Make 6 dozen cookies.