In a medium bowl, combine cooked chicken breast, shredded cheese, ranch dressing, diced green onions, and diced bell pepper. Mix thoroughly.

Place a skillet over medium heat and pour in olive oil. Heat for 1-2 minutes until shimmering.

Lay a tortilla in the preheated skillet, spoon a quarter of the chicken filling onto one half, and fold the other half over.

Cook for 3-4 minutes until golden brown, then flip and cook for another 2-3 minutes until the cheese melts.

Let the quesadilla cool for 2 minutes before slicing into wedges. Serve with extra ranch dressing on the side.