Rinse and slice green peppers, onion, and mushrooms into thin pieces. Add 1 tablespoon vegetable oil to a large pan or cast-iron skillet over medium-high heat. Once hot, add sliced vegetables and season with salt and pepper. Cook for 5-6 minutes until vegetables are tender and set aside.

In the same pan, add another tablespoon of vegetable oil. Once hot, add Gary's Quick Steak Pre-Sliced Sirloin Beef. Add Worcestershire sauce, garlic powder, salt, and pepper and stir. Cook until meat is browned. Add vegetables back to the pan and stir together.

Preheat oven to 400 degrees Fahrenheit. Slice each hoagie bun and spread a thin layer of mayonnaise to the inside of each bun. Fill each bun with cooked sirloin and vegetables. Add mozzarella on top of sirloin and vegetables.

Melt butter in a small bowl and use a basting brush to top each bun with butter. Wrap each sandwich with aluminum foil.

Bake in the oven at 400 degrees Fahrenheit for 12-17 minutes until cheese is melted.