Pre-heat oven to 180°C or 350°F. Line a muffin tin with parchment paper liners.
In a medium bowl, combine the dry ingredients (reserving 1 tbsp of oat flour for later).
In a large bowl, whisk together the wet ingredients (except for the blueberries).
Add the dry ingredients into the wet ingredients and stir until just combined.
In a small bowl, toss 1 cup of blueberries and 1 tbsp of oat flour together, then gently fold them into the batter. This will prevent the muffins from turning blue.
Divide batter evenly between 9 muffin liners. Top with remaining blueberries.
Bake for 18 -25 minutes. To test if they're ready, insert a toothpick. If the toothpick comes out clean or with just a few tiny crumbs attached, then the muffins are ready!
Transfer pan to a wire rack to cool for 8-10 minutes. Then remove muffins from the pan and place them on the wire rack to cool for another 5-10 minutes. Enjoy!