Preheat the oven to 425°F. Lightly spray a muffin tin with non-stick spray, or line with paper liners. Set aside.
In a small bowl, prepare the topping. Stir together the brown sugar, rolled oats and cinnamon. Set aside.
In a medium bowl, whisk together the oil, sugar, brown sugar, eggs, yogurt, buttermilk and vanilla until combined.
In a large bowl, whisk together the flour, oat flour, baking soda, baking powder and salt.
Make a well in the center of the dry ingredients and pour in the liquid mixture. Stir until just combined, do not over-mix.
Toss the blueberries with 1 tablespoon of flour to coat them and gently fold them into the muffin batter.
Divide the batter between the 12 muffin cups, filling until almost full.
Sprinkle the topping onto the muffins. Bake for 5 minutes at 425°F, then lower the oven temperature to 350°F, and continue to bake for another 15-18 minutes, until a toothpick inserted in the center of a muffin comes out clean.
Allow to cool in the muffin tin for at least ten minutes before removing the muffins.
Store in an airtight container at room temperature for 5 days, or freeze for up to 3 months.