Preheat oven to 325º F.
Combine bananas, oil, yogurt, eggs and sugar in a large mixing bowl. Add flours, salt, baking soda and vanilla. Stir just until combined.
Spray a large loaf pan (I use a 9x5 glass pan) with cooking spray. Pour banana mixture inside loaf pan and bake for about 60-85 minutes. If you use two smaller pans, the cook time will need to be adjusted. It will probably take around 45 minutes.
Use the toothpick method to check and see if it's cooked in the middle. Cool on rack and then remove from pans. Slice and enjoy!