Preheat the oven to 400°F. Butter a 12-cup standard muffin pan or line the pan with baking cups. Set aside. Combine the flour, oat bran, whole wheat flour, baking powder, and salt in a large mixing bowl. Whisk to blend. In a separate bowl, whisk the banana, oil, egg, brown sugar, and milk until evenly blended. Make a well in the dry ingredients and add the liquids. Stir well, until just a few streaks of dry ingredients remain, then stir in the blueberries until evenly mixed. Divide the batter equally among the cups. Sprinkle a little sugar on top of each, if you like. Bake for 10 minutes, then reduce the heat to 375°F and bake for 12 minutes more.

Cool the muffins in the pan on a rack for 5 minutes. Remove the muffins from the pan and continue to cool. Serve warm or at room temperature.