Combine first 4 ingredients. Add margarine and egg whites; stir well. Cover and let stand 1 hour. (Batter will be thin.)
Spoon batter by level teaspoonfuls, 2 inches apart, onto cookie sheets coated with cooking spray. Bake at 400° for 5 minutes or until edges are browned. Let cool on cookie sheets 1 minute. Remove from cookie sheets. Let cool completely on wire racks.