Heat gas or charcoal grill. In large bowl, mix ground beef, bread crumbs, milk, pizza seasoning, salt and garlic. Shape mixture into 12 (4-inch) sausage-shaped rolls. Flatten each to 1/4-inch thickness to form patties.
In medium bowl, mix 1/4 cup of the pizza sauce, the onion and olives. Spoon about 1 tablespoon mixture evenly onto 6 patties, spreading to within 1/2 inch of edges. Top with remaining patties; pinch edges to seal.
Place meat loaves on grill; cover grill. Cook with medium heat 10 to 14 minutes, turning several times, until thermometer inserted in meat loaves reads 160°F (avoid inserting in filling). Brush meat loaves with remaining 1/4 cup pizza sauce and top each with cheese strips; cook 1 minute longer or until cheese is melted.