Start by gathering all your ingredients.

Place your skillet over medium heat and add the olive oil.

Add the sliced onions (and bell peppers, if using) to the skillet. Sauté until they are soft and caramelized, about 5 to 7 minutes.

Push the vegetables to one side of the skillet and add the sliced beef. Season with salt and pepper, and cook until browned, about 3 to 5 minutes.

Mix the beef with the sautéed onions and peppers.

Lay the cheese slices over the beef mixture in the skillet. Cover for a minute to allow the cheese to melt perfectly.

While the cheese melts, split the hoagie rolls and toast them lightly in the skillet.

Fill each toasted roll with the cheesy beef mixture. Serve hot.