Prepare the Meatballs:
Preheat your oven to 400°F (200°C).
In a mixing bowl, combine the ground beef, breadcrumbs, Parmesan, egg, garlic, oregano, basil, onion powder, salt, and pepper. Mix until just combined.
Roll the mixture into 1-inch meatballs and place them on a baking sheet lined with parchment paper.
Bake for 15–20 minutes, or until browned and cooked through.
Simmer the Sauce:
While the meatballs bake, heat the marinara sauce in a large skillet over medium heat.
Once the meatballs are done, transfer them to the skillet with the sauce. Simmer for 5–7 minutes to let the flavors meld.
Toast the Rolls:
Preheat your oven's broiler.
Slice the sub rolls and spread a little butter on the insides if desired. Place them under the broiler for 1–2 minutes, until lightly toasted.
Assemble the Subs:
Fill each roll with meatballs and a generous amount of marinara sauce.
Top with shredded cheese and place the assembled subs on a baking sheet.
Broil for 1–2 minutes, just until the cheese melts and starts to bubble.
Serve:
Garnish with fresh parsley if desired and serve the subs hot. Pair with a side of chips, salad, or fries for a complete meal.