Combine first 5 ingredients in a medium bowl; make a well in center of mixture. Combine milk and oil, stirring with a wire whisk. Add to dry ingredients, stirring just until dry ingredients are moistened.
Beat egg white at high speed of an electric mixer until stiff peaks form. Gently fold beaten egg white into batter.
Coat an 8-inch square waffle iron with cooking spray; allow waffle iron to preheat. Pour batter onto hot waffle iron, spreading batter to edges. Bake 3 to 4 minutes or until steaming stops. Cut waffle into 4 squares.