01 -
Preheat oven to 375°F. Lightly grease a 9 x 13-inch baking dish or line with parchment paper.
02 -
In a large mixing bowl, blend ground beef, Italian-style breadcrumbs, eggs, milk, chopped onion, minced garlic, salt, black pepper, and Italian seasoning until evenly combined.
03 -
Place a large sheet of parchment paper or foil on your work surface and press the beef mixture into a rectangle, approximately 1/2 inch thick.
04 -
Spread shredded mozzarella evenly over the meat, leaving a 1-inch border. Place baby spinach in an even layer if using, and sprinkle grated Parmesan across the top.
05 -
Carefully roll the mixture from the short end, using the parchment to help lift. Pinch seams and ends to seal tightly.
06 -
Carefully lift and transfer the rolled loaf, seam side down, into the prepared baking dish.
07 -
Spoon 1 cup marinara sauce evenly over the top of the meatloaf.
08 -
Bake in the center of the oven for 55 to 65 minutes, or until the internal temperature reaches 160°F.
09 -
Remove from the oven and let rest for 10 minutes before slicing. Serve with extra marinara sauce as desired.