1.Preheat the oven to 350°F. Combine beef, salt, pepper, Worcestershire, and garlic powder in a 9x13-inch rimmed baking dish, mixing thoroughly, then pressing into a flat, even layer. Bake for 20 minutes. Drain the liquid and set the cooked beef aside. Wash and dry baking dish.
2.Slice the rolls in half horizontally. Place the bottom half in the same baking dish. Place the cheese on the rolls, followed by the beef and onions. Top with the remaining rolls. Brush the tops of the rolls with melted butter.
3.Bake for 20 minutes, or until the bread is golden brown and the cheese is melted. Slice into individual sliders, then serve.