In a large roasting pan (disposable aluminum foil pan is fine) place brisket . Pour beer over the meat, and put onion sections on top then season with garlic, salt and pepper. Next combine the barbecue sauce, molasses and liquid smoke and pour over the roast. Cover with aluminum foil.
Place pan on the oven, and bake for about 6 to 8 hours until beef is fork tender. Remove it from the oven and let stand for about 10 minutes before slicing into 1/8 inch slices.