Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper or a silicone mat.
In a large mixing bowl, combine the ground beef, breadcrumbs, Parmesan, milk, eggs, 1/2 cup marinara sauce, parsley, garlic, oregano, salt, and pepper.
Mix by hand until ingredients are just incorporated. Do not overwork the meat.
Place half of the meat mixture onto the prepared baking sheet and flatten it into a 9x5 inch rectangle.
Place the mozzarella sticks lengthwise down the center of the meat rectangle, leaving a 1-inch border on all sides.
Place the remaining meat mixture over the cheese and press the edges firmly to seal the cheese completely inside the loaf.
Spread the remaining 1/4 cup of marinara sauce evenly over the top and sides of the meatloaf.
Bake for 55 to 60 minutes, or until the internal temperature reaches 160°F (71°C) on a meat thermometer.
Remove from the oven and allow the meatloaf to rest for 10 minutes before slicing to ensure the cheese center remains intact.