- Preheat the oven to 350°F. Lightly oil a standard 9 x 5 inch metal loaf pan. Dust the pan with flour and tap out the excess.
- Mix the cranberries and granulated sugar together in a small bowl. Set aside. In a separate bowl, mix the flours, brown sugar, baking powder, baking soda, and salt. Set aside.
- Whisk together the orange zest, juice, oil, egg, and vanilla extract. Add to the flour mixture and stir just until the ingredients are barely combined. Fold in the sugared cranberries. Add a little milk, if needed, to make a soft consistency that will drop from the spoon when it is gently shaken. Transfer the batter to the prepared pan and level the surface.
- Bake until well risen, golden, and firm to the touch, about 1 1/4 hours. A toothpick inserted in the center should come out clean. Let cool until just warm, then run a knife around the inside of the pan and unmold the loaf onto a wire rack to cool completely. Serve sliced and buttered.