Preheat oven to 400°F. Line a baking sheet with parchment paper or coat with cooking spray.
Combine flour, oats, sugar, baking powder, orange zest, baking soda and salt in a large bowl. Using a pastry cutter or two knives, cut butter into flour mixture until it resembles coarse crumbs. Add berries to flour mixture and toss carefully to coat.
Whisk buttermilk, egg and vanilla together in a small bowl. Create a well in center of flour and berry mixture. Pour in buttermilk mixture and gently mix just until dough forms.
Flour hands and place dough on a well-floured work surface. Gently knead twice just to form into a ball. Pat into an 8-inch circle, about 3/4-inch thick. With a floured spatula or sharp knife, cut into 8 even wedges. Place wedges on prepared baking sheet, leaving space between wedges. Brush tops with additional buttermilk and sprinkle with additional sugar, if desired. Bake 14 minutes or until light golden brown. Cool on wire rack.