Pre-heat oven to 350 degrees and spray the inside of a glass baking dish (8x8 or larger)
Mash bananas in a large bowl
Add in brown sugar, eggs, salt, vanilla, baking powder, baking soda, cinnamon and nutmeg. Mix until combined.
Stir in milk and oats. Add walnuts, if desired.
Pour oat mixture into baking dish and cover with foil.
Bake for 30 minutes then remove foil. Bake for an additional 15 minutes or until center is solid and edges are golden brown.
Serve warm as is or pour some cold milk over it.