Preheat the oven to 325°F (165°C). Lightly grease a 9-by-13-inch baking dish and spread the beef cubes in an even layer.
In a bowl, whisk together the brown gravy mix, dry onion soup mix, condensed mushroom soup, and water until combined.
Pour the gravy mixture over the beef and turn the cubes to coat. Cover the dish tightly with foil.
Bake for 2½ to 3 hours, until the beef is fork-tender. If desired, stir once halfway through and reseal the foil.
Rest for 5 to 10 minutes, then serve with mashed potatoes, rice, or egg noodles.
