Preheat the oven to 350 degrees and grease two 81/2 x 41/2 loaf pans. the center comes out clean.
In the bowl of a food processor combine the flours, baking soda and brown sugar with the butter until the mixture resembles coarse sand. Transfer the mixture to a large mixing bowl. Stir in ¾ cup plus 2 Tbsp. of the oats.
Add the milk, molasses, and the Guinness.
Stir to combine (the dough will be very wet). Evenly divide the dough between the two loaf pans.
Sprinkle the tops with the remaining 2 Tbsp. oats. Bake for 40 - 45 minutes until the bread is nicely browned and a cake tester inserted in the center comes out clean.
Let the loaves cool on a cooling rack. I like to run a butter knife around the edges of the pan so that the loaves come out more easily.