In large saucepan, combine applesauce and chocolate. Heat over low heat, stirring frequently, until chocolate is melted. Remove from heat; cool slightly. Add sugar and applesauce; mix well. Stir in egg whites and vanilla; mix well. Add combined oats, baking powder and salt; mix well. Spread evenly in prepared pan. Bake 22-25 minutes or until center is set and eges pull away from sides of pan. Cool completely. Sprinkle with powdered sugar before serving, if desired. Cut into 24 bars. Store loosely covered. Makes 24 servings.