Preheat oven to 350 degrees F (180 degrees C).
Grease the loaf with oil and flour and keep aside.
Toast walnuts and chop coarsely.
Combine the flour, sugar, baking powder, baking soda, salt, cinnamon, and nuts. keep aside.
Combine the mashed bananas, eggs, melted butter, vanilla. With a wooden spoon,lightly fold wet ingredients into dry ingredients just until combined and the batter is thick.
Do not over mix the batter it may yield tough,hard,rubbery bread.)
Transfer batter into prepared pan.
Bake at 350 degrees 55-60 minutes.