Coat one side of each tortilla with cooking spray. Place tortillas, sprayed sides down, on a cutting board or parchment paper. Sprinkle with chicken, feta cheese, red onion, cucumber, grape tomatoes, olives, parsley, and oregano. Drizzle with dressing. Fold tortillas in half, pressing gently.
Heat a large nonstick skillet over medium heat for 1 minute. Cook quesadillas, two at a time, over medium heat for 4 to 6 minutes or until light brown, turning once. Remove quesadillas from skillet; place on a baking sheet. Keep warm in a 300 degree F oven. Repeat with remaining quesadillas. To serve Cut each quesadilla into three wedges. Makes 4 servings.