1. Heat grill.
2. For the yogurt sauce, combine yogurt, feta cheese, dill and 1/4 teaspoon salt; set aside.
3. Arrange sweet peppers and zucchini on cookie sheet. Combine oil, 1/4 teaspoon salt, and black pepper in cup; brush onto both sides of vegetables. Grill peppers over medium heat 6 to 7 minutes per side and zucchini 3 to 5 minutes per side, until tender. Grill pitas 3 minutes per side, until toasted.
4. Spread one side of each pita with 2 tablespoons yogurt sauce; spoon vegetables in center of pitas and fold in half. Serve with remaining yogurt sauce. Garnish with dill, if desired. Makes 4 servings.