In a small bowl, whisk together the dry ingredients including the oats, flour, cinnamon, baking soda, and salt.
Preheat oven to 350 degrees F, line large baking sheet with parchment paper and spray with cooking spray.
In a large bowl, mash bananas. Add melted butter, vanilla extract, add egg; mix well. Add the dry ingredients; stir to combine. Add walnuts and raisins, mixing well.
Using a large spoon (just under 1/4 cup), place batter on previously prepared sheet and flatten with the back of a spoon into medium sized cookies. Note: Cookies do not spread, so you can place closer together.
Bake for 20 minutes or until walnuts start to brown a bit.
Remove from the oven and let cookies cool for a few minutes, then transfer onto a cooling rack to finish cooling.