Preheat the oven to 300°F.
Add the stewing beef to an 8×8 inch baking dish.
Sprinkle the dry onion soup mix over the beef.
Spoon the cream of mushroom soup over the beef.
Stir to coat the beef, then spread into an even layer.
Cover the baking dish with heavy duty aluminum foil, making sure it’s well sealed at the edges.
Bake for 3 hours, or until the beef is fork tender.
Carefully remove the foil (it will be hot!), give the beef a stir, and serve.