Start by pre-heating the oven to 350 degrees. Prepare a loaf pan (9x5 inches) by cutting a piece of parchment paper to fit the bottom and 2 sides of the pan, leaving an inch or two extra to act as handles to remove bread from pan. Butter the paper to stick to the pan.
Add first four dry ingredients (flour, oats, salt, baking soda) to bowl and blend with a whisk. Then mix in the brown sugar until thoroughly incorporated.
Combine wet ingredients (molasses, Guinness, buttermilk and melted butter) and pour into dry ingredients, stirring by hand with a spoon or spatula until blended, but don’t over mix.
Spread the dough into the prepared loaf pan with a spatula, pressing carefully into the corners. Cut a line down the middle of the dough with the spatula or a blunt knife to provide a vent to expand. Sprinkle the top of the dough with the reserved oats.
Bake at 350 degrees for 55-65 minutes or until a toothpick inserted in the center comes out clean.
Remove the bread from the oven and allow to cool. Slice and enjoy.