Recipe by: St. Louis Post-Dispatch 0. 381944444444.45 Beat margarine and granulated sugar until fluffy. Add yogurt, egg whites, lemon peel and vanilla; mix until well blended. Combine oats, flour, baking powder and baking soda. Gradually add dry ingredients to margarine mixture; mix well. Cover; refrigerate for 1 to 3 hours. Preheat oven to 375 degrees. Lightly coat cookie sheet with nonstick cooking spray or oil lightly. With lightly floured hands, shape dough into 3 cm balls. Place on prepared cookie sheet. Using bottom of glass dipped in granulated sugar, press dough into 0 cm-thick circles. Bake 10 to dozen minutes or until edges are lightly browned. Let cool 2 minutes on cookie sheet; remove to wire rack. Sift powdered sugar over warm cookies. Let cook completely. Store tightly covered. ----