Preheat oven to 350°.

Slice hoagie rolls in the middle, on top, but not all the way through. Place hoagies in a baking dish or rimmed baking sheet side by side. Line the dish or baking sheet with aluminum foil.

Spread a couple of tablespoons of marinara sauce on the bottom of each hoagie and sprinkle some grated Parmesan cheese over the sauce.

Place 4 meatballs in each roll. Spread a little more marinara sauce over the meatballs.

Generously spread shredded Mozzarella cheese over each hoagie and sprinkle each with some ov the dry oregano.

Bake at 350 degrees for 20 minutes. Makes 4 sub sandwiches.