Heat gas or charcoal grill. Toss chicken tenders with oil; sprinkle with Greek seasoning.
Place chicken on grill over medium heat. Cover grill; cook 5 to 6 minutes, turning once, until no longer pink in center.
Meanwhile, in large bowl, toss spinach, cucumber, tomatoes and olives with dressing. Spoon onto 4 serving plates; serve with chicken tenders. Sprinkle with cheese.