Special equipment: a 4-ounce (1/2 cup) ice cream or cookie scoop
Put an oven rack in the center of the oven. Preheat the oven to 350 degrees F. Line 2 baking sheets with parchment paper. Set aside.
In a medium bowl, whisk together the flour, cinnamon, baking powder, baking soda, and salt. In a stand mixer fitted with a paddle attachment, beat the butter and sugars together until light and fluffy, about 1 minute. Add the egg and vanilla and beat until smooth. With the machine running, gradually add the flour mixture. Add the oats, cranberries and chocolate chunks. Mix until just incorporated (dough will be stiff). Using a 4-ounce cookie scoop, scoop slightly rounded mounds of the dough into 12 (2-inch-diameter) balls. Arrange 6 balls of dough, spaced evenly apart, on each baking sheet. Using the back of a spoon, flatten the tops slightly and bake until the cookies are slightly golden on the edges, about 13 to 15 minutes. Allow the cookies to cool on the baking sheet for 20 minutes before serving.