Preheat oven to 400 degrees. Line muffin tins with paper liners and lightly coat with cooking spray.
Place oats in a food processor, pulse 5-6 times until oats resemble coarse meal. Place in a large bowl.
Weigh or lightly spoon flours into dry measuring cups; level with a knife. Add flours and next 5 ingredients (through salt) to oats; stir well. Make a well in center of mixture.
Combine buttermilk and next 3 ingredients (through eggs). Add to flour mixture and stir until just moist.
Toss blueberries with flour and gently fold into batter. Spoon batter into 16 muffin cups. Sprinkle with sugar evenly over batter.
Bake at 400 degrees for 20 minutes or until muffins spring back when touched lightly in center.
Remove from pans immediately and cool on a wire rack.