Preheat oven to 375F. Grease muffin tin with non-stick cooking spray.
In a small bowl soak oatmeal in milk for 30 minutes.
In a large bowl stir bran, flax, flour, baking powder, baking soda, salt, nutmeg and cinnamon.
In a blender add eggs, bananas, yogurt, canola oil, and brown sugar and blitz until smooth.
Pour banana mixture and soaked oats over dry ingredients. Fold together with a rubber spatula, adding in blueberries just before fully incorporated.
Using a large spoon fill blueberry banana muffin batter into greased tins.
Bake for 25 minutes and let cool before serving.
Store leftovers in an air-tight container in the freezer for up to one month.