To make this Philly Cheese Meatloaf gluten-free, replace the panko breadcrumbs with certified gluten-free breadcrumbs or gluten-free panko. Confirm that the Worcestershire sauce, provolone cheese, mozzarella cheese, ground beef, olive oil, seasonings, garlic, eggs, onion, and bell pepper are gluten-free and free from cross-contact. Some Worcestershire sauces and packaged cheeses may contain gluten-based additives or be processed in shared facilities, so check labels carefully. Use clean utensils, bowls, pans, and prep surfaces to prevent cross-contamination.