Mix ground beef, breadcrumbs, Parmesan cheese, garlic powder, onion powder, dried oregano, and egg in a large bowl.
Combine everything well to form the meatball mixture.
Shape the mixture into balls, about 1 inch in size.
Place them on a baking sheet lined with parchment paper.
Bake the meatballs at 375°F until cooked, which should take about 15-20 minutes.
Make sure to turn them once halfway through the cooking time.
Heat marinara sauce in a large saucepan over medium heat.
Add cooked meatballs to the sauce, letting them simmer for 10 minutes to absorb the flavors.
Place meatballs on sub rolls, topping them with sliced provolone cheese.
Toast the sandwiches in the oven until the cheese melts.