Grease and flour a 9" x 13" baking pan, and set aside.
In a small bowl, pour the hot water over the oatmeal, and set aside for a few minutes. In another bowl, mix the cocoa, flour, baking soda and salt together, set aside. In a large bowl, combine the oil with the two sugars.
In a separate bowl, beat the egg whites until soft peaks form. Pour the whites into the sugar mixture. Stir the flour mixture into the batter. Once combined, add the oatmeal and the vanilla to the batter.
Pour into the baking pan and bake for 30 - 35 minutes.