1. Heat oven to 350°F. Grease or line 12 (2 3/4 in.) muffin cups with paper baking cups. Combine oats and buttermilk; let stand.
2. Combine flour, baking powder, cinnamon, baking soda and salt; mix well. Combine butter, brown sugar, egg and orange peel. Stir in oat mixture; mix well. Add to flour mixture; stir just until dry ingredients are moistened. Fold in raisins.
3. Spoon batter into prepared muffin cups. Bake at 350°F for 25 to 30 minutes or until toothpick inserted in center comes out clean.