Preheat your oven to 375°F (190°C). Grease a muffin tin or line with paper muffin liners.
In a large bowl, mix together wheat bran and buttermilk. Let stand for 10 minutes.
In another bowl, beat together oil, egg, sugar, and vanilla. Add to the bran mixture and stir well.
Sift together flour, baking soda, baking powder, and salt. Stir into bran mixture until just blended. Fold in raisins.
Spoon batter into prepared muffin cups, filling each about ⅔ full.
Bake in preheated oven for 15 to 20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Cool on a wire rack before serving.