In a large bowl mix together flour, baking soda, baking powder, cinnamon if using, and salt. Set aside.
In a large bowl using a hand mixer or a stand mixer fitted with the paddle attachment beat together butter, peanut butter, brown sugar, and granulated sugar for 3-4 minutes until creamy. Add eggs and vanilla extract and beat until combined. Add flour mixture and beat on low speed just until combined. Don’t over mix. Add oats and chocolate chips, and keep beating on low just until combined. The less you mix, the softer the cookies will be.
Preheat oven to 350°F/180°C. Line two pans with parchment paper and set aside.
Drop rounded balls of dough, the size of 2 tablespoons of dough per cookie, onto prepared baking sheets (each cookie weighs about 45 grams), spacing them 3 inches apart. Bake for 12-14 minutes, until cookies are lightly browned at the edges and center is still soft. Allow to cool for 10 minutes in pan, then transfer cookies to a wire rack to cool completely.
Store cookies in an airtight container at room temperature for up to 3 days or in the fridge for one week (but serve them at room temperature). Cookies can also be frozen for up to 3 months. To thaw, leave on the counter, still covered, or overnight in the fridge.