Gather all ingredients.

Whisk together flour, oats, baking powder, salt, baking soda, and 1/4 cup of the sugar in a large bowl until combined.

Cut butter into flour mixture with your fingers or a pastry cutter until dough resembles coarse meal.

Add raisins, orange zest, and 3/4 cup plus 1 tablespoon of buttermilk; stir until just combined.

Transfer dough to a lightly floured work surface; pat dough into a 7-inch circle, about 3/4-inch thick. Line a baking sheet with parchment.

Using a floured bench scraper or knife, cut dough circle into 8 wedges; place wedges on the prepared baking sheet, spacing about 1 inch apart. Alternatively, scoop 8 (1/3-cup) mounds of dough onto a parchment-lined baking sheet, about 2 inches apart. Brush each scone evenly with remaining 2 tablespoons buttermilk, and sprinkle with remaining 1 tablespoon sugar. Place baking sheet in freezer, and freeze until chilled, about 30 minutes.

Preheat the oven to 425 degrees F (220 degrees C).

Bake scones in the preheated oven until bottoms and tops are golden, about 20 minutes.