Place an oven rack in the center of the oven and preheat to 350℉. Line two baking sheets with parchment paper or silpats.
In a medium bowl, whisk together flour, cinnamon, baking powder, baking soda, and salt.
In a stand mixer fitted with the paddle attachment, beat the butter and both sugars until light and fluffy. Add the egg and vanilla and beat until smooth. With the machine running on low, gradually add the flour mixture. Now add the oats, cranberries, and chocolate chunks. Mix until just incorporated. The dough will be stiff.
Using a regular ice cream scoop or a ¼-cup measure, scoop 12 (2-inch) mounds of dough onto the prepared baking sheets. You’ll have 6 cookies per sheet and you want them spaced evenly apart. Use the back of a spoon or just your hand to flatten them slightly.
Bake 13 to 15 minutes, until the cookies are slightly golden on the edges. Allow them to cool on the baking sheet for about 20 minutes before transferring them to a cooling rack (or eating them outright).