Gather all ingredients.
Preheat the oven to 375 degrees F (190 degrees C). Grease 12 muffin cups or line with paper muffin liners.
Mix wheat bran and buttermilk together in a large bowl; let stand for 10 minutes.
Meanwhile, beat brown sugar, oil, egg, and vanilla together in a separate bowl until light and fluffy; stir into buttermilk mixture.
Sift flour, baking soda, baking powder, and salt together; stir into buttermilk mixture until just blended. Fold in raisins; spoon batter into the prepared muffin cups, filling each ⅔ full.
Bake in the preheated oven until tops spring back when lightly pressed, about 15 to 20 minutes. Cool in the tin briefly, then transfer to a wire rack to cool completely. Enjoy!
