Preheat air fryer to 375°F.

In a bowl, mix cooked chicken, diced bell pepper, diced onion, and taco seasoning until well combined.

Place one tortilla on a clean surface. Spread half of the chicken mixture over one half of the tortilla, then sprinkle half of the cheese on top of the mixture.

Fold the tortilla in half to cover the filling.

Lightly spray both sides of the quesadilla with cooking spray.

Place the quesadilla in the air fryer basket. Cook for 4 minutes.

Carefully flip the quesadilla and cook for an additional 4 minutes, or until golden brown and the cheese is melted.

Remove from the air fryer, let cool for a minute, then slice into wedges and serve.