1. Pre-heat oven to 400 degrees.
2. Prepare muffin tin by spraying with a non- stick cooking spray or line with paper muffin cups.
3. Pour the buttermilk into a large glass mixing bowl.
4. Add the oats to the buttermilk and stir to moisten. Let the oats soak in the buttermilk for about 15 minutes.
5. While the oats are soaking, sift together the flour, baking powder, baking soda and salt. (If you don't own a sifter, a strainer or colander works. Just sift the ingredients back and forth so it's well mixed.)
6. After the oats have soaked for 15 minutes add the egg whites, brown sugar and the oil to the oatmeal/buttermilk bowl. Using a rubber spatula, stir until the brown sugar has completely dissolved.
7. Pour the wet ingredients into the dry ingredients. Stir with the rubber spatula until all the ingredients are combined together well. (Do not over-mix.)
8. Fill each muffin cup 2/3 full with the batter.
9. Bake the muffins 16 - 18 minutes or until a toothpick inserted in the center comes out clean.