Slice the beef into thin strips if not already done. Cut onions and bell peppers into thin slices. Keep everything ready before cooking. This helps you cook quickly and keeps the beef tender and juicy.

Heat oil in a skillet over medium heat. Add sliced onions and peppers. Cook until soft and slightly golden. Stir often to avoid burning. This step brings out sweet flavors and adds depth to the sandwich.

Push vegetables to one side of the pan. Add beef to the empty space. Season with salt, pepper and garlic powder. Cook for a few minutes. Stir gently until beef is browned but still juicy.

Mix the beef with cooked vegetables. Spread the mixture evenly in the pan. Place cheese slices on top. Let the cheese melt slowly. Cover the pan for faster melting if needed.

Cut hoagie rolls and spread butter inside. Toast them lightly in another pan. This adds crunch and prevents soggy bread. Warm bread makes the sandwich even more delicious.

Fill each roll with the hot beef and cheese mixture. Serve immediately while warm. Enjoy the rich flavors and soft texture. Each bite is cheesy, juicy and full of comfort.