Preheat the oven to 210 degrees C. Grease a baking tray.
In a medium bowl, stir together the oat flour, bran, salt, baking powder, cream of tartar, cinnamon and sugar. Cut in the butter until the mixture resembles coarse crumbs. Stir in the egg, milk and vanilla until mixture is well blended.
Drop by heaping tablespoonfuls onto the prepared baking tray. Bake for 12 to 15 minutes in the preheated oven, biscuits should be lightly browned.