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 them sit for about 10 minutes.
In another bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large bowl, beat the sugar, egg, oil, and vanilla extract until well combined.
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. Do not overmix.
Gently 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 of a muffin comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.