Step 1
Preheat oven to 350 degrees F (175 degrees C).
Step 2
Place a large roasting pan over medium-high heat and sear beef brisket fat side down at first until browned on all sides about 3 minutes per side. Remove brisket and set aside.
Step 3
Place onion slices into the bottom of the roasting pan; pour 1 can beef broth 1 can French onion soup and 1 can beer over the onions.
Step 4
Lay the brisket into the roasting pan; pour remaining cans of beef broth French onion soup and beer over the brisket. Cover the roasting pan with a lid.
Step 5
Bake in the preheated oven for 3 hours. Remove from oven and let stand for 30 minutes.
Step 6
Remove cooled brisket from roasting pan and wrap tightly in aluminum foil. Pour pan juices and onion into a food storage container and cover tightly with a lid. Refrigerate beef and pan juices overnight.
Step 7
The next day preheat oven to 350 degrees F (175 degrees C). Pour pan juices and onion into a 9x13-inch baking dish.
Step 8
Unwrap the brisket cut away any visible fat and slice thinly across the grain of the meat. Place brisket slices into the pan juices.
Step 9
Return to oven and bake until pan juices are thickened and meat is hot about 45 more minutes.