In a large bowl, combine ground beef, breadcrumbs, egg, Parmesan cheese, garlic powder, Italian seasoning, salt, and pepper. Mix until just combined and form meatballs.

Heat a skillet over medium heat and add olive oil. Carefully place meatballs in skillet, cooking for 10-12 minutes until browned and cooked through.

Pour marinara sauce into a saucepan over medium-low heat. Stir occasionally until heated through, about 5 minutes.

Transfer cooked meatballs to sub rolls and spoon warm marinara sauce over them.

Preheat broiler to high, sprinkle cheese over each sub, and broil for 2-3 minutes until the cheese is bubbly.

Garnish with fresh basil, slice in half if desired, and serve immediately with extra marinara sauce.