01 - Preheat oven to 400°F and line a baking sheet with parchment paper.
02 - In a large bowl, combine ground turkey, breadcrumbs, Parmesan, egg, milk, garlic, parsley, oregano, salt, and pepper. Mix gently until just combined.
03 - Shape mixture into 16 small meatballs (approximately 1.5 inches each) and arrange on the prepared baking sheet. Bake for 15 to 18 minutes until lightly browned and cooked through.
04 - While meatballs bake, heat olive oil in a large skillet over medium heat. Add marinara sauce and crushed red pepper flakes, bringing to a simmer. Add baked meatballs and simmer for 10 minutes, turning occasionally to coat.
05 - Preheat broiler. Split sub rolls and toast lightly if desired. Place 4 meatballs with sauce into each roll.
06 - Top meatballs with mozzarella and Parmesan cheeses. Place subs under broiler for 1 to 2 minutes until cheese is melted and bubbly.
07 - Garnish with fresh basil leaves if preferred. Serve immediately.