Preheat a stovetop or outdoor grill over medium heat.
Warm the flour tortillas, to make them easier to work with, on the stove in a hot skillet. Just a few seconds on each side.
Spread each tortilla with BBQ sauce and sprinkle evenly with shredded cheese. On one side of the tortilla sprinkle with sliced chicken, red onion, scallions, and cilantro. Fold over each quesadilla to form a half moon shape.
Grill the quesadillas (2 at a time) on the preheated grill. You can grease them lightly with cooking spray to make it easier. Grill for about 2 to 4 minutes per side, or until grill marks form and the cheese has melted through. Slice and serve hot with a side of BBQ sauce for dipping. Enjoy!