In a large bowl, combine the shredded chicken, crumbled bacon, cheddar cheese, mozzarella cheese, and ranch seasoning mix. Mix well until all ingredients are evenly coated with the seasoning.
Heat a large skillet over medium heat and add half of the olive oil.
Place one tortilla in the skillet and spread about 1 cup of the chicken mixture evenly over half of the tortilla.
Fold the tortilla in half to cover the filling and cook for about 3-4 minutes, or until the bottom is golden brown.
Carefully flip the quesadilla and cook for an additional 3-4 minutes on the other side until it is golden and the cheese is melted.
Remove the quesadilla from the skillet and repeat the process with the remaining tortillas and filling, adding more olive oil as needed.
Slice each quesadilla into wedges and serve warm with sour cream and salsa, if desired.