4(6-inch)sub rolls, split partially open lengthwise
Preheat the broiler in your oven and adjust a rack to the upper-middle position. Meanwhile, in a large skillet, melt the butter, Add the onion and cook until softened and golden, about 8 minutes. Stir in the garlic and oregano and cook for a minute, until it smells fragrant. Add the A-1 sauce and the beef, stirring well to coat the beef with the sauce and onion/butter mixture. Cook until the meat is heated through, about 2 minutes. Season with salt and pepper.
Place the sliced rolls on a rimmed baking sheet. Divide the beef mixture among the rolls. Top with the cheese and broil until the cheese is melted, about 2 minutes (don’t even take your hand off the oven door handle – stand right there so they don’t burn!). Serve immediately.