Mash the bananas. Place the bananas, eggs, oats, oil, maple syrup, vanilla, baking soda, baking powder, cinnamon and kosher salt in a blender. Blend everything on high for a minute or two until a smooth batter forms.
Add the blueberries to the blender; gently stir until combined.
Place 12 muffin cups into a muffin tin and pour the batter divided evenly between the cups. To see more blueberries on the tops of the muffins, we pressed a few extras into the tops of the muffins. Sprinkle the tops with turbinado sugar (or extra oats and gently press them down).
Bake for about 30 to 35 minutes until a toothpick comes out clean. Remove from the muffin tin and allow them to cool a few minutes before serving. Store refrigerated for about 1 week, or frozen for up to three months.