Preheat oven to 400°F (200°C). Grease a muffin tin or line with paper muffin liners.
In a large bowl, combine oat bran, whole wheat flour, brown sugar, baking powder, baking soda, and salt. Stir in nuts and blueberries.
In another bowl, whisk together buttermilk, vegetable oil, egg, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Spoon the batter into the prepared muffin tin, filling each cup about ⅔ full.
Bake for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.