Preheat your oven to 350 degrees Fahrenheit and line a baking sheet with parchment paper.
In a large bowl, mix together the rolled oats, applesauce, and peanut butter until fully combined.
Scoop the mixture and form into cookie shapes, placing them on the prepared baking sheet.
Gently press down on each cookie to flatten slightly.
Sprinkle with cinnamon if desired.
Bake for 10 to 12 minutes, or until the cookies are set.
Allow the cookies to cool completely on the baking sheet to finish setting up.