Preheat oven to 350 F. Generously spray an 11x7 inch glass Pyrex baking dish with cooking spray. In a medium bowl, combine oats, evaporated milk, egg white, raisins, walnuts and 3 tablespoons sugar, making sure all the ingredients are wet and evenly distributed.

Using a spatula, spread the mixture in an even, thin layer in the baking dish. Sprinkle remaining tablespoon of sugar evenly over the top. Bake until the edges and bottom are golden brown, about 45 to 50 minutes. Cut into 9 bars while they are still hot, allow to cool slightly, and remove from dish to continue cooling.

Store in airtight containers or individual baggies for easy grab and go access.