Brush chicken breasts with oil, and sprinkle evenly with Greek seasoning.
Grill chicken breasts, covered with grill lid, over medium-high heat (350° to 400°) 6 to 8 minutes on each side or until chicken is done. Let chicken stand 10 minutes; cut into 1/4-inch-thick slices.
Place sliced chicken down center of warmed flatbread slices. Top with Low-Cal Dilled Yogurt Dressing, cucumber, tomato slices, and lettuce; roll up. Serve immediately.
*Pita bread rounds may be substituted for flatbread. Line warmed pita rounds with Low-Cal Dilled Yogurt Dressing, lettuce, tomato slices, and cucumber slices. Fill with sliced chicken, and serve immediately.