Prepare the Baking Station : Position oven racks in the upper and lower thirds of your oven and preheat to 375°F (190°C). Line your half-sheet pans with parchment paper for easy cleanup and to prevent sticking.
Combine Dry Ingredients : In the small bowl, whisk together the white whole-wheat flour, rolled oats, baking powder, cinnamon, nutmeg, and salt. Blending these now ensures the spices are evenly distributed throughout the dough.
Cream Butter and Sugar : In the large mixing bowl, beat the softened butter and packed brown sugar with an electric mixer on medium speed for about 2 minutes. The mixture should become light, fluffy, and pale in color.
Incorporate Wet Ingredients : Add the egg and vanilla extract to the creamed butter mixture. Beat on low speed until just combined, scraping down the sides of the bowl with a spatula as needed to ensure everything is evenly incorporated.
Form the Dough : Pour the dry ingredient mixture into the wet ingredients. Mix on low speed until a cohesive dough forms. Be careful not to overmix. Gently fold in the dried cranberries with the silicone spatula.
Portion and Bake : Drop rounded tablespoons of the cookie dough about 2 inches apart onto the prepared pans, yielding about 8 cookies per pan. Bake for 9 to 11 minutes, rotating the pans top-to-bottom and front-to-back halfway through. The cookies are done when the edges are set and golden brown.
Cool and Set : Remove the pans from the oven and let the cookies rest on the hot pans for 3 minutes to firm up slightly. Afterward, carefully transfer them to a wire rack to cool completely.