Preheat the oven to 400 degrees F. Grease a 12-cup muffin tin (or line with muffin/cupcake liners.) Set aside.
In a large bowl, whisk 1 ½ cups of the flour, oats, brown sugar, baking powder, cinnamon, and salt together. Set aside.
In a separate bowl, whisk the milk, cooled melted butter, eggs, and vanilla together until combined.
Blend the wet mixture into the dry mixture using a wooden spoon. Mix until just combined. Don't over mix.
Toss the blueberries with 1 Tablespoon of flour. Fold coated blueberries into the batter. Divide the batter evenly among the prepared 12 muffin cups.
Bake for 18 minutes or until a toothpick inserted in the center comes out clean. Remove muffins from the oven and let cool in the pan for 15 minutes before serving. Enjoy!