Adjust oven rack to center position and preheat oven to 350°F. Line baking sheets with parchment paper and set aside.
In a medium bowl, whisk together the whole wheat pastry flour, baking powder, salt, and nutmeg; set aside.
In a large bowl, use an electric mixer to cream the butter until smooth. Add the sugars and beat on medium high for 2 to 3 minutes or until fluffy. Blend in the eggs, one at a time. With the mixer on low, gradually stir in the flour mixture, and then the oats and cranberries, until just combined, scraping the bowl as necessary to ensure that all ingredients are incorporated.
Scoop cookie dough using a tablespoon (or a 1-tablespoon-sized cookie scoop) and roll into balls (with an approximately 1-inch diameter). Space the balls at least 1 inch apart on prepared baking sheets. Bake for 14 to 16 minutes or until the cookies are set in the center and the edges are just starting to turn golden brown, taking care not to overbake. Allow to cool for 2 minutes on the pan before removing to a wire rack to finish cooling. Once completely cool, store in an airtight container.