Preheat oven to 400°F (200°C).
Combine flour, oat bran, sugar, baking powder, salt and raisins. Cut in chilled butter until mixture resembles coarse crumbs. Set aside.
Beat egg. Add milk and orange rind. Add liquids to dry ingredients all at once. Stir lightly with a fork until moistened. Knead 10 times.
Pat dough into two circles about 3/4″ (2 cm) thick on greased baking sheet. Brush tops with milk and sprinkle lightly with sugar. Score each circle into 6 wedges.
Bake on upper rack in oven for 15 minutes. Serve warm with butter.