In a large bowl, whisk together the flour, cinnamon, baking soda, and salt. Put aside.
Using a stand mixer fitted with the paddle attachment (I love my KitchenAid), or an electric mixer, cream together the butter with the sugars for 1-2 minutes until well combined. Add the egg and vanilla and mix until fully combined.
Gradually mix in the flour mixture and continue mixing until just combined, then mix in the oats, chocolate chips and cranberries until fully combined. It is important to scrape down the sides of the bowl as needed.
Cover the cookie dough and refrigerate for 30 minutes.
During this time, preheat the oven to 350°F. Line a large baking sheet with parchment paper or a silicone baking mat, then set aside.
Once the dough is chilled, remove it from the refrigerator. Using a tablespoon, scoop the dough and roll into balls. Place on prepared baking sheet leaving a little room between each cookie. Gently press down to flatten just slightly.
Bake one sheet at a time for 10-12 minutes or until the edges of the cookies are lightly golden and the top is set. Remove from the oven and cool on the baking sheet for 5 minutes before transferring the cookies to a wire rack to finish cooling.
Before measuring out flour lay out some parchment. Using a large spoon mix up the flour and scoop into measuring cup. With the back of a butter knife level excess flour and add to bowl. Then you can pour the excess flour on parchment back into flour container.
Chilling allows for a fluffier cookie, if you prefer yours to be thinner chilling can be cut down or out altogether.
Cookies store well at room temperature in an air-tight container, best when eaten in the first few days.