In a mixing bowl, combine flour and sugar. Cut in butter until crumbly. Set aside 3/4 cup for topping. Add the baking powder, milk and egg yolks to remaining mixture; mix well. Beat egg whites until soft peaks form; fold into batter.
Pour into a greased 13-in. x 9-in. x 2-in. baking dish. Sprinkle with blueberries and reserved crumb mixture. Bake at 350 degrees F or 176 degrees C for 30-35 minutes or until golden brown and a toothpick inserted near the center comes out clean.