Preheat & Prep: Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or grease with nonstick spray.
Mix Dry Ingredients: In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
Mix Wet Ingredients: In another bowl, whisk together milk, oil, eggs, and vanilla extract until smooth.
Combine: Gradually mix the wet ingredients into the dry ingredients, stirring gently until just combined (do not overmix).
Prepare Blueberries: Toss blueberries with 1 tbsp flour to prevent them from sinking. Gently fold them into the batter.
Fill Muffin Cups: Divide the batter evenly among the muffin cups, filling each about ¾ full. Sprinkle with coarse sugar if desired.
Bake: Bake for 18-22 minutes or until a toothpick inserted in the center comes out clean.
Cool & Serve: Let muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.