Coat the grill rack with cooking spray. Prepare the grill to medium heat.
In a small mixing bowl, combine the yogurt, cucumber, lemon juice, mint, and ½ teaspoon of the garlic, stirring well to mix. Cover and refrigerate until ready to use.
In a medium mixing bowl, combine the turkey, oregano, salt, lemon pepper, and remaining 1 teaspoon of garlic, stirring well to mix. Gently form the mixture into 8 small patties, about ¾-inch thick. When grill is ready, grill burgers for 5 minutes on each side, or until cooked through.
Place pitas on the grill and heat for 1 minute on each side. Cut pitas in half and fill each with a burger, sliced tomatoes and yogurt sauce.