Preheat oven to 375°F.

In a bowl, combine ground beef, breadcrumbs, egg, garlic powder, onion powder, Italian seasoning, salt, and pepper. Mix until well combined.

Form the mixture into 1-inch meatballs and place on a baking sheet.

Bake meatballs for 20 minutes or until cooked through.

In a saucepan, heat marinara sauce over medium heat. Add cooked meatballs to the sauce and simmer for 10 minutes.

Slice hoagie rolls in half lengthwise and spread butter on the cut sides. Toast in the oven for 3-5 minutes until lightly golden.

Place meatballs and sauce on the bottom half of each hoagie roll. Top with shredded mozzarella cheese.

Broil the assembled subs for 2-3 minutes until cheese is melted and bubbly.

Serve hot with extra marinara sauce if desired.