Preheat your 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.
In another bowl, whisk together milk, beaten egg, vegetable oil, and vanilla extract.
Add the wet ingredients to the dry ingredients and stir until just combined. Do not overmix.
Spoon the batter into the prepared muffin tin, filling each cup about ⅔ full.
Bake for 15-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.