Preheat the oven to 350 degrees and spray a 9x5 inch loaf pan with non-stick spray. I like organic coconut oil spray.
Mash the bananas in a large bowl with the back of a fork.
Add the ground flax seeds, milk, coconut oil, maple syrup and vanilla to the bowl and mix well to incorporate.
Add the sugar, oats, baking soda, baking powder, salt, flour, and walnuts (if using) to the bowl and mix well to incorporate.
Pour the batter into the loaf pan evenly. Add toppings like non-dairy chocolate chips or walnuts, if desired.
Place the loaf pan into the oven on the center rack and bake for 50-60 minutes until a toothpick inserted into the middle of the loaf comes out clean.
Remove from the oven and let cool for 20 minutes.
Slice and enjoy!