Preheat the oven to 450°F (230°C) and lightly grease a 9x13-inch baking dish with 1 tablespoon of olive oil.
In a large mixing bowl combine the ground sirloin, bread crumbs, grated Parmesan, chopped parsley, dried oregano, crushed red pepper, a generous pinch of kosher salt and black pepper, 1 tablespoon olive oil, and the egg; mix until just combined.
Coat your hands with a little olive oil and roll the mixture into 2-tablespoon meatballs (about 10–12). Place them in the prepared baking dish in a single layer.
Bake the meatballs for 15 minutes until the exterior is lightly crisp but the centers are not fully cooked.
Remove from the oven, spoon the marinara sauce evenly over the meatballs, sprinkle with shredded mozzarella, and return to the oven; bake another 15–20 minutes until meatballs are cooked through (internal temperature 160°F) and cheese is melted.
Meanwhile, cook whole wheat pasta according to package directions (or prepare spaghetti squash) and drain.
Serve the meatballs and sauce over the cooked pasta or spaghetti squash.
Optional: To make one large “giant” meatball, form the mixture into an oval, bake 35–45 minutes until cooked through, add cheese during the last 10 minutes of baking, then serve with pasta.