I found this recipe in Martha's 2001 Holiday Cookies magazine and have been making it every Christmas since. It is among my most requested cookies during the holiday season. (*Prep time does not include chill time)
In a medium bowl, whisk together flour, salt, cinnamon, baking powder, and baking soda. Set aside.
In a small bowl, whisk together the vanilla, milk, and eggs. Set aside.
In the bowl of an electric mixer fitted with the paddle attachment, combine the butter with both sugars, and beat on medium speed until light and fluffy. Reduce speed to low, gradually add milk mixture, and beat well. Add the flour mixture, and beat until just combined. Remove bowl from the electric mixer, and stir in the oats and cranberries. Place dough in the refrigerator until firm, at least 2 hours or overnight.
Preheat the oven to 350 degrees. Line several baking sheets with parchment paper and set aside. Shape 2 tablespoons of dough into a ball; place on one of the prepared sheets. Repeat with the remaining dough, placing 3 inches apart. Press with the bottom of a glass to flatten dough into 2-inch diameter rounds.
Bake until golden but still soft in center, 16 to 18 minutes, rotating halfway through. Remove from oven; transfer with parchment to a wire rack to cool. Store in an airtight container at room temperature for up to 1 week.