Mix mayonnaise, yogurt and 1 teaspoon of the Seasoning in small bowl until well blended. Cover. Refrigerate until ready to serve.
Mix ground chicken, feta cheese, onion, garlic powder, oregano and remaining 1 1/2 teaspoons Seasoning in large bowl until well blended. Shape into 4 patties.
Grill burgers over medium heat 4 to 6 minutes per side or until burgers are cooked through (internal temperature of 165°F).
Serve burgers on toasted rolls topped with the yogurt sauce, lettuce and tomato and cucumber slices.