Weigh or lightly spoon 5 ounces flour (about 1 cup) into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients in a medium bowl, stirring with a whisk. Drizzle butter and juice over flour mixture, stirring with a fork until moist (mixture will be crumbly). Reserve 1/2 cup oat mixture. Press remaining oat mixture into bottom of an 11 x 7inch glass or ceramic baking dish coated with cooking spray.
Combine granulated sugar and 2 tablespoons flour in a medium bowl, stirring with a whisk. Add egg white and next 3 ingredients, stirring with a whisk until blended. Stir in cherries. Spread cherry mixture over prepared crust; sprinkle reserved oat mixture evenly over filling.
Bake at 325° for 40 minutes or until edges are golden. Cool completely in pan on a wire rack. Cut into bars.