Mix the chopped bacon, chicken, onion and barbecue sauce in a bowl together.
Preheat griddle or quesadilla press over medium heat.
Arrange a tortilla on a flat surface. Spread half the bbq chicken mixture evenly over it, leaving a 1" border. Top with zesty ranch dressing, cheese, and some avocado. Finish off with another tortilla.
Press until golden and the cheese melts, flipping once on a griddle.