In a mixing bowl, combine the shredded chicken, crumbled bacon, cheddar cheese, Monterey Jack cheese, and ranch dressing. Mix well to combine.

Heat a skillet over medium heat. Place one tortilla in the skillet and spread a portion of the filling mixture on half of the tortilla.

Fold the tortilla over to cover the filling and cook for 3-4 minutes until the bottom is golden brown.

Carefully flip the quesadilla and cook for another 3-4 minutes until the other side is golden and the cheese is melted.

Remove from the skillet and repeat with the remaining tortillas and filling.

Cut the quesadillas into wedges and serve warm with optional toppings such as chopped green onions, sour cream, and salsa.