Preheat oven to 350°F (177°C). Line a large cookie sheet with parchment paper or a silicone baking mat.

Add quick oats to a food processor. Pulse oats until they become very small and fine and start to partially become flour consistency. See photo in post for reference. I pulsed mine on high for about 30 seconds. If you are unsure if your oats are fine enough, it's better to pulse them a little longer. The smaller they are, the crispier the cookies will be.

Add peanut butter, maple syrup and cinnamon into the oat mixture. Pulse a few seconds until everything is evenly combined.

Using a 1 tbsp cookie scoop, scoop dough onto the prepared cookie sheet, spacing the dough balls about 2 inches apart. Roll each dough between your palms and then flatten the dough balls into thin round disks. You want the cookies to be fairly thin, about ⅛ inch thick and no more than 3/16 inch thick. The thinner the cookies are, the crispier they will be. The cookies do not spread much during baking, so shape them as you want the final outcome to be. I usually flatten the cookies first with my palm a few times and then smooth around the edges with the back of a spoon to make the cookies round.

Bake cookies for 10-11 minutes or until the surface looks done and the edges turn light brown. The browner the cookies get, the crispier they will be but you want to be careful not to burn them. Let cookies cool completely on the baking sheet before removing them. They will crisp up further as they cool.