Fold the empty half of the tortilla over the filling to form a half-moon shape. Cook for 2-3 minutes until the bottom is golden and crispy, then carefully flip and cook the other side for 2-3 minutes.
Remove from the skillet and repeat with the remaining tortillas, chicken, veggies, and cheese, adding more oil or butter as needed.
Slice each quesadilla into wedges and serve hot with salsa, sour cream, or guacamole on the side. Enjoy your chicken quesadillas!