Preheat oven to 375°F (190°C). Line baking sheets with parchment paper or silicone liners.
Whisk together the flour, baking soda, baking powder, and salt. Set aside.
Using an electric mixer on medium speed, beat the butter until light and creamy. Gradually add the sugars and mix well. Add the egg and vanilla. Mix well.
Reduce mixer speed to low. Gradually add the flour mixture, mixing just until combined or a few streaks of flour remain. Stir in cranberries, pecans, and oats.
Drop the dough by tablespoonfuls onto the prepared pans, placing the cookies about 2 inches apart. Bake for 8 to 10 minutes or until lightly browned.
Cool on the pans on a wire rack for 2 minutes. Then, transfer the cookies from the pan to wire racks to finish cooling.
Melt white chocolate and transfer to a zip-top bag (or use a piping bag). Cut the corner of the bag and use to drizzle white chocolate onto cookies. Alternatively, simply dip the cookies partially in the melted white chocolate.
To store. Place the cooled cookies in an airtight container. Store at room temperature up to 3 days. They can be refrigerated to extend their shelf-life a couple of days; just be sure the container is airtight so they don't dry out. To keep the cookies looking their best, place waxed paper between layers of the cookies.
To freeze baked cookies. If you want to freeze the baked cookies, they'll be best frozen without the white chocolate glaze. The drizzled cookies may still taste fine after thawing, but the chocolate on top is likely to look a little worse for wear. Place the cookies in an airtight, freezer-safe container or bag. Properly stored, the cookies should keep in the freezer up to 3 months. Thaw overnight in the refrigerator or for an hour or so at room temperature.
To freeze cookie dough. To freeze the cookie dough, portion the cookies as directed in the recipe. Place the balls of dough on a baking sheet, and freeze just until solid (2-3 hours). Once frozen, transfer the cookies to an airtight, freezer-safe container or bag. They should keep up to 3 months. When you're ready to bake, place the cookies on a baking sheet and bake as directed in the recipe, adding a couple of minutes to the baking time.