Put the sausage and bacon in a large cast iron skillet over medium heat. Cook, turning to brown evenly, until bacon is crisp, about 5 minutes. Remove bacon from pan and set it aside.

Add a 1/4 cup of the beer to the skillet and continue cooking the sausage until cooked through, about 10 minutes more. Remove the sausage from the pan and set aside.

Add the potatoes and onion to the skillet, along with another 1/4 cup beer. Cook, stirring and adding more beer as needed, until potatoes are tender, about 20 minutes. Season with salt and pepper, to taste.

Cut the sausages into 1/4-inch-thick rounds and stir into the potato mixture along with the barbecue sauce. Transfer to a serving dish and crumble the bacon over the top. Sprinkle with parsley and serve.