Soak 8 wooden skewers in water. In a small bowl, combine the yogurt, cucumber, dill and half the garlic; season to taste with salt and pepper. Refrigerate.
Preheat a grill or grill pan to medium-high. In a medium bowl, combine the beef, remaining garlic, chopped parsley and cumin. Add salt and pepper to taste. Divide the beef mixture into 4 sections. Roll each section into a 6-inch log. Thread each log lengthwise onto two parallel skewers. Wrap your index finger and thumb around the log and lightly squeeze from top to bottom to make 4 indented rings. Rub the beef kebabs with olive oil and grill for 6 to 8 minutes on each side, or to desired doneness. Top each kebab with the yogurt sauce and parsley leaves and serve on a pita.