Preheat your oven to 400°F (200°C) and grease a muffin tin or line with paper liners.
In a large mixing bowl, whisk together the oat bran, whole wheat flour, brown sugar, baking powder, baking soda, and salt.
In another bowl, combine the milk, egg, vegetable oil, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.
Divide the batter evenly among the muffin cups.
Bake for 15-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for a few minutes before transferring to a wire rack to cool completely.