Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Sprinkle chicken with Greek seasoning; add to skillet. Cook chicken 6 to 8 minutes or until lightly browned, stirring occasionally.
While chicken cooks, spread hummus evenly over pita rounds. Arrange chicken, lettuce, and remaining ingredients evenly on one half of each pita round. Fold pitas over filling; secure with wooden picks.