Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, combine the mashed bananas, melted coconut oil or butter, egg, rolled oats, baking soda, cinnamon (if using), vanilla, and salt. Mix until well combined.
To the mixture add in your whole wheat flour, mixing until just combined.
Using a spoon or cookie scoop, drop spoonfuls of the dough onto the prepared baking sheet, spacing them about 2 inches apart. You can flatten slightly with a spoon or fork if you wan't, but I left mine as it.
Bake for 12-15 minutes, or until the cookies are set and lightly golden around the edges.
Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
Enjoy!