"This is based on Mrs. Sigg's Snickerdoodles (it's an excellent recipe; you should try it). These cookies came out soft with a touch of ginger. If you don't have oat flour use a food processor or blender to pulverize oatmeal."
Beat 1 1/2 cups sugar, butter, eggs, and vanilla extract together in a large bowl until smooth and creamy.
Sift all-purpose flour, oat flour, cream of tartar, and baking soda together into a bowl. Beat 1/2 of the flour mixture into butter mixture; and remaining flour mixture and beat until dough is just combined. Cover the bowl with plastic wrap and refrigerate until chilled, about 30 minutes.
Preheat oven to 400 degrees F (200 degrees C). Line baking sheets with parchment paper.
Whisk 2 tablespoons sugar, cinnamon, and ginger together in a shallow bowl.
Roll chilled dough into 1 1/2-inch balls and roll each ball in cinnamon-sugar mixture to coat. Place coated dough 2-inches apart on prepared baking sheets.
Bake in the preheated oven until golden and set, 9 to 11 minutes. Cool on the baking sheet for 5 minutes before removing to a wire rack to cool completely.