Line muffin tin(s) with paper cups, or spray with cooking spray.
Mix together buttermilk, honey, oil, and egg whites in small bowl.
In large bowl, combine oats, oat bran, flour, baking powder, and salt. Make a well in center of dry ingredients. Pour in milk mixture and blueberries. Stir until combined, being careful not to overmix.
Pour batter into muffin cups and bake for 25 minutes, or until a toothpick inserted into center comes out clean.