Preheat oven to 350 degrees. Line a baking pan with parchment paper or baking mat. Mash bananas in a medium bowl. Give the oatmeal a quick pulse in a food processor or blender, for about 1-2 seconds; But don't turn the oatmeal into a fine flour; You just want the oats to be broken down a bit. (You could also just use quick oats which are old fashioned oats already broken down a bit). This process is important for your cookies to hold together.
Pour oats into the bowl with the bananas and add cinnamon or chocolate chips if desired. Spoon preparation onto the lined baking sheet and mold the cookies with your fingers; The dough will not spread, so shape the cookies as you desire. (You could also scoop the batter with an ice cream scoop and release batter straight onto the pan, which is what I prefer). Transfer to oven and bake for 10-15 minutes or until cookies are just set and are turning lightly golden brown.