Mix first 7 ingredients together and set aside. In large bowl beat margarine, brown sugar, yogurt, egg whites and vanilla with an electric mixer until blended mixture will look curdled. Gradually beat in flour mixture until blended. Cover and refrigerate at least 2 hours or until firm enough to handle.
Preheat oven to 375 degrees. Pour granulated sugar in small bowl. Roll tablespoonfulls of dough into 1 inch balls. Roll in granulated sugar to coat. Place 1 inch apart on ungreased cookie sheets. Bake 8-10 minutes until firm. Cool on wire racks. Store in airtight container for up to 3 weeks.
Makes 48 cookies.