Preheat the oven to 350° F. Spray or line a baking sheet.
In a medium bowl, add the bananas and mash with a fork until very smooth.
Add in the oats, flax seeds (if using), and chocolate chips, and gently stir together until incorporated.
Scoop one tablespoon of batter out of the bowl and form them into a flat cookie shape. These cookies will not flatten while cooking. Place on a baking sheet.
Place the baking sheet in the oven, and bake for 15-20 minutes or until set and golden brown on the bottom. Let cool on the pan for 2 minutes.
Serve and enjoy!