1Heat gas or charcoal grill. In large bowl, mix beef, cheese, olives, oregano and mint. Shape mixture into 4 patties, about 1/2 inch thick.
2Place patties on grill over medium heat. Cover grill; cook 10 to 12 minutes, turning once, until meat thermometer inserted in center of patties reads 160°F.
3Cut burgers in half. Fill each pita pocket with burger half, cucumber, onion and tomato slices; drizzle with yogurt.