In the bowl of a stand mixer (or large bowl with hand mixer), cream together the butter and sugars until smooth and fluffy.
Add in the egg and vanilla, and mix, scraping the sides and bottom of the bowl in between.
In a large bowl, combine the flour, baking powder, baking soda, salt, cinnamon, and oats.
Add the dry ingredients to the mixer, and stir until combined.
Add in the cranberries and white chocolate chips. Stir by hand.
Refrigerate the dough for at least 30 minutes.
Preheat oven to 350 degrees and line 2 sheet pans with parchment paper.
Scoop the dough using a 1 1/2 TBSP. scoop, and place 2 inches apart on the baking sheet. Add a few extra chips/cranberries to the top, if desired.
Bake for 10-12 minutes, or until the edges are slightly golden. Allow to cool on the sheet pan for 5 minutes, before transferring to a wire rack to cool completely.