A cup of quick-cooking oats makes these moist muffins even more substantial. A touch of spicy cinnamon in the batter pairs nicely with the sweet, juicy blueberries.
Preheat oven to 350 degrees. Line a standard 12-cup muffin tin with baking cups. In a medium bowl, whisk together flour, oats, baking powder, salt, and cinnamon. In a separate bowl, whisk together sugar, eggs, butter, and milk. Stir wet ingredients into dry ingredients, then stir in blueberries.
Divide batter evenly between muffin cups, adding a scant 1/4 cup to each. Sprinkle with sanding sugar, if desired. Bake until tops spring back when lightly touched, about 20 minutes. Cool in pans 5 minutes, then remove to wire rack to cool completely.