Preheat your oven to 350°F and make sure your baking rack is in the middle of the oven.
In a large mixing bowl, whisk together the flour, oats, cinnamon, baking soda, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl using an electric mixer, mix the room temperature butter and the sugars together for 1-2 minutes or until fluffy and well-combined. Mix in the egg, then add in the vanilla extract.
Slowly add in the dry ingredients and continue mixing until just combined, making sure to scrape down the sides of the bowl as needed. Then mix in the white chocolate chips and dried cranberries until thoroughly combined. (You will likely want to use the heat of your hands here to incorporate all of the ingredients and get the dough to form better)
Line large baking sheets with parchment paper or silicone baking mats and divide the dough into 14 balls and roll them into balls — they don't need to be perfectly round (see picture). Leave a bit of room between each ball of cookie dough so they have some room to spread.
Bake at 350°F (180°C) for 13-17* minutes or until the edges of the cookies are lightly browned and the top is set — I always bake mine for 15 minutes. (Yours could take a few more or a few less depending on your oven) Remove cookies from the oven and cool on a baking sheet for 5-10 minutes before transferring them to a wire rack to cool completely.
Store in an air-tight container on the counter.
If you're having trouble getting your dough to hold together for some reason, you can try adding a tiny bit of room temperature water (about a tsp. at a time) to add some moisture to the dough and help it hold together. Cookie dough balls can be frozen for up to 3 months. Bake from frozen for an additional 2-3 minutes. You can also bake the cookies and then freeze them for up to three months, but let them come to room temperature before serving.