Waldorf Chicken Wraps

Name: Waldorf Chicken Wraps
Ingredients: 1 cup nonfat plain yogurt or 3/4 cups nonfat Greek-style yogurt; 2 tablespoons mayonnaise; 1 tablespoon lemon juice; 2 teaspoons Dijon Mustard; 1/4 teaspoon salt; 1 teaspoon minced thyme; 1 pound cooked, skinless chicken breast cut into 1/2-inch cubes; 1/2 cup seedless grapes, sliced in 1/2; 1/4 cup toasted, coarsely chopped walnuts; 1 medium apple, cored and diced (about 3/4 cup); Freshly ground black pepper; 5 large leaves Romaine lettuce, rinsed and patted dry; 5 whole-wheat wraps, about 8 inches in diameter