Step 1: Prepare the Meatballs : In a large bowl, combine ground turkey, breadcrumbs, Parmesan, egg, garlic, parsley, oregano, salt, and pepper. Mix gently until just combined—overmixing can make meatballs tough. Form the mixture into 1.5-inch meatballs and place them on a baking sheet lined with parchment paper. Optionally, brush with olive oil for a golden exterior.
Step 2: Cook the Meatballs : Oven method: Bake at 400°F (200°C) for 18–20 minutes, or until fully cooked (internal temperature 165°F / 74°C). Stovetop method: Heat 1–2 tbsp olive oil in a skillet over medium heat and cook meatballs, turning occasionally, for 10–12 minutes until golden and cooked through.
Step 3: Make the Marinara Sauce : Heat 1 tbsp olive oil in a saucepan over medium heat. Sauté chopped onions until translucent, about 3–4 minutes. Add garlic and cook 30 seconds more. Add crushed tomatoes, basil, oregano, red pepper flakes (if using), salt, pepper, and sugar. Simmer gently for 15–20 minutes, stirring occasionally, until sauce thickens.
Step 4: Assemble the Subs : Slice sub rolls lengthwise without cutting all the way through. Place 3–4 meatballs in each roll. Spoon marinara sauce generously over the meatballs. Top with shredded mozzarella or provolone cheese.
Step 5: Melt the Cheese : Place assembled subs on a baking sheet and bake at 375°F (190°C) for 5–7 minutes, or until cheese melts and rolls are slightly toasted.