Preheat your oven to 400°F (200°C). Grease a muffin tin or line with paper muffin liners.
In a large bowl, mix together the oat bran, flour, brown sugar, baking powder, baking soda, and salt.
In another bowl, whisk together the milk, egg, 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 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow to cool in the tin for a few minutes, then transfer to a wire rack to cool completely.