In a slow cooker, combine beef strips, sliced onion, green and red bell peppers.
In a small bowl, whisk together beef broth, garlic powder, salt, and black pepper. Pour this mixture over the beef and vegetables in the slow cooker.
Cover and cook on low for 6 hours until the beef is tender.
Preheat your oven to 400 degrees F. Split the hoagie rolls and place two slices of provolone cheese in each. Toast in the oven for about 5 minutes, or until the cheese is melted.
Using tongs, place the beef and pepper mixture onto the cheesy hoagie rolls. Serve hot.