1 Preheat the oven to 350°F. Grease a 9"x 9"x 2" baking pan. In a large bowl, combine the oats, all-purpose flour, whole-wheat flour, baking powder, salt, and cinnamon and milk.
2 In a perfectly clean large bowl, beat the egg whites with an electric mixer set on high speed until they form soft peaks. Beat in the sugar, 1 tablespoon at a time, until the whites form stiff peaks, then beat in the vanilla. Using a rubber spatula, gently fold the egg whites into the oat mixture, then spread the batter evenly in the pan.
3 Bake for 30 to 35 minutes or until the top is brown and a toothpick inserted in the center comes out clean. Let cool for 10 minutes in the pan, then transfer to a wire rack and let cool to room temperature.