Heat oven to 350°F. Lightly spray bottom only of 13 x 9-inch baking pan with cooking spray. In large saucepan, heat oil and chocolate over low heat until chocolate is melted, stirring frequently. Remove from heat. Stir in granulated sugar and applesauce until sugar is dissolved. Stir in egg whites and vanilla until completely blended. Add combined oats, flour, baking powder and salt; mix well. Spread evenly into pan. Bake 22 to 25 minutes or until edges begin to pull away from sides of pan. Cool completely in pan on wire rack. Cut into bars. Store tightly covered. Sprinkle with powdered sugar just before serving.