Preheat your oven to 400°F (200°C). Grease a muffin tin or line with paper liners.
In a bowl, combine the oats and milk. Let sit for 10 minutes.
In another bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large bowl, beat the egg and brown sugar until well combined. Stir in the oil and vanilla extract.
Add the soaked oats and milk mixture to the wet ingredients and mix well.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Fold in the blueberries.
Divide the batter evenly among the muffin cups.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.