Preheat oven to 375°F (190°C) and place a rack in the middle position. Line baking sheets with parchment paper or silicone baking mats.

In the bowl of a stand mixer or a large mixing bowl (if using a hand mixer), beat the unsalted butter until pale and fluffy, about 2 minutes.

Add the dark brown sugar and beat until light and fluffy, about 2 more minutes.

Add the eggs one at a time, beating briefly after each addition until each is fully incorporated. Add the pure vanilla extract and mix until combined.

In a separate large bowl, whisk together the old-fashioned rolled oats, all-purpose flour, baking soda, and salt until evenly combined.

Add the dry mixture to the wet mixture and mix just until the flour is incorporated and no large streaks of flour remain. Do not overmix.

Stir in the white chocolate chips (the entire 11-ounce bag) and the dried cranberries with a sturdy spoon until evenly distributed through the dough.

Drop rounded spoonfuls or use a cookie scoop to portion dough onto the prepared baking sheets, spacing cookies a few inches apart to allow for spreading.

Bake on the middle rack until the cookies have spread, are set at the edges, and are beginning to brown, about 8–10 minutes.

Remove the sheets from the oven and let the cookies cool on the baking sheet for about 5 minutes. Transfer cookies to a wire rack to cool completely.

Store cooled cookies in an airtight container at room temperature for up to about 4 days.