In a medium bowl, combine the shredded chicken and buffalo sauce. Mix until the chicken is well coated.
In another bowl, mix the cheddar cheese, mozzarella cheese, garlic powder, onion powder, salt, and pepper.
Heat a large skillet over medium heat and add the olive oil.
Place one tortilla in the skillet and spread half of the buffalo chicken mixture evenly over the tortilla.
Sprinkle half of the cheese mixture on top of the chicken.
Top with another tortilla 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 until the other side is golden and the cheese is melted.
Remove from the skillet and let it cool for a minute before cutting into wedges.
Repeat the process with the remaining tortillas and filling.
Serve warm with ranch dressing for dipping and garnish with chopped green onions if desired.