Begin by heating a tablespoon of olive oil in a large skillet over medium-high heat.

Add the sliced onions and green bell pepper to the skillet and sauté for about 3 to 5 minutes. If using mushrooms, add them now and continue to cook for another 3 minutes, or until the vegetables are tender.

Push the sautéed vegetables to one side of the skillet. Add the ground beef to the other side, breaking the meat apart as it cooks, until no longer pink, about 5 to 7 minutes. Mix in the vegetables.

Stir in the garlic powder, Worcestershire sauce, salt, and black pepper. Cook for an additional 2 minutes to blend the flavors.

Reduce heat to low, place the cheese slices over the beef mixture, cover the skillet, and let the cheese melt for about 2 to 3 minutes.

Slice the hoagie rolls lengthwise without cutting all the way through.

Transfer the beef and vegetable mixture into each hoagie roll evenly.

Optionally, toast the hoagie rolls in a skillet for a minute before serving. Enjoy hot.