In a large mixing bowl or stand mixer, cream together unsalted butter, granulated sugar, and light brown sugar until light and fluffy, about 2-3 minutes. Then add in the egg and vanilla extract, mixing until well combined.

In a separate bowl, whisk together the baking powder, baking soda, salt, cinnamon, and all-purpose flour. Gradually incorporate the dry mixture into the wet ingredients until just combined.

Fold in old-fashioned oats, white chocolate chips, and dried cranberries. Ensure even distribution throughout the cookie dough.

Cover the dough with plastic wrap and refrigerate for 30-60 minutes to prevent spreading during baking.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Drop rounded balls of dough onto the prepared baking sheet, leaving 2-3 inches between each. Optionally, press each ball down slightly.

Bake for 10-12 minutes until the edges are just set but the centers look slightly underbaked.

Let the cookies rest on the baking sheet for 3-5 minutes before transferring to a wire rack to cool completely.