In 10-inch skillet, cook ground beef, onion, garlic, oregano and 1/4 teaspoon of the salt over medium-high heat 5 to 7 minutes, stirring frequently, until beef is thoroughly cooked. Drain. Stir in olives.
Meanwhile, in medium bowl, stir together cucumber, tomato, yogurt, dill and remaining 1/4 teaspoon salt.
On each of 4 individual serving plates, Spoon 1/4 of beef mixture on half of each pita. Top each with yogurt mixture; fold other half of pita over filling. Serve with remaining yogurt mixture.