Heat olive oil in a large skillet over medium heat.
Add ground beef and cook until browned, breaking it apart with a spoon.
Stir in diced onion and green bell pepper, cooking until softened.
Season with garlic powder, salt, and black pepper.
Add Worcestershire sauce and ketchup, stirring to coat the beef mixture.
In a small bowl, mix beef broth and cornstarch, then pour into the skillet.
Simmer for 3–5 minutes until the sauce thickens.
Reduce heat to low, place cheese slices on top, and let them melt.
Scoop the beef mixture onto toasted hoagie rolls and serve immediately.