In large bowl, beat butter, sugar and lemon peel with electric mixer until creamy. Gradually add combined flour, oats, baking powder and salt; mix well. Divide dough in half; wrap each half in plastic wrap. Chill 1 hour or until firm. Heat oven to 325° F. Remove one portion of dough from refrigerator. On lightly floured surface, roll dough into 10-inch square. With sharp knife, cut into 30 rectangles (each about 3 inches long and 1 inch wide). Transfer rectangles to ungreased cookie sheets; prick each rectangle three times with a fork. Repeat with remaining dough. Bake 18 to 20 minutes or until lightly browned. Cool 1 minute on cookie sheets; remove to wire rack. Cool completely. Store tightly covered.