In a large mixing bowl, combine the ground turkey, egg, breadcrumbs, Parmesan cheese, minced garlic, chopped parsley, dried oregano, onion powder, and a sprinkle of salt and black pepper. Mix until just combined, then form into 16-18 meatballs.

Heat olive oil in a large skillet over medium heat. Add meatballs, brown for 2-3 minutes each side until golden brown. Remove and set aside.

Pour marinara sauce into the skillet, warm it up, then nestle browned meatballs into the sauce. Simmer covered for 12-15 minutes until cooked through.

Preheat your broiler and place sub rolls on a baking sheet. Broil for 60-90 seconds until light golden.

Fill each toasted roll with 4-5 meatballs and marinara sauce. Top with shredded mozzarella.

Return assembled subs to the broiler for 2-4 minutes until cheese melts and bubbles. Let rest for a minute before serving.