Preheat oven to 375°F.
Place sliced beef in a large mixing bowl. Season beef with chili powder, cumin, onion powder, garlic powder, salt and pepper. Toss beef to coat with seasonings. Set aside.
Cut a long slit down the center of each hoagie roll, with your fingers remove bread from the center of each roll, forming a hollowed out "boat".
Spread a tablespoon of mayo in the hollowed out insides of each hoagie roll.
Place two slices of Provolone cheese into the bottom and along sides of each hollowed out hoagie roll. Set rolls aside.
In a large skillet heat butter over medium heat.
Add sliced onions and sliced bell pepper, cook until soft, about 3-5 minutes. Remove from pan, set aside.
Add 2 more tablespoons butter to the skillet. Add seasoned sliced beef. Cook until beef is cooked through.
Place a generous amount of cooked beef strips into each hollowed out prepared hoagie roll.
Top with a layer of shredded Mozzarella cheese.
Add a layer of grilled onions & peppers.
Top with a layer of shredded Mozzarella cheese.
Add another layer of beef, then another layer of peppers and grilled onions.
Top with a final layer of shredded cheese.
Place sandwiches on a cookie sheet and bake in the oven for 10 minutes until cheese melts.
Switch oven temperature to broil and toast sandwiches until golden brown and cheese is melted and bubbly.
Serve immediately.