01 - In a medium bowl, combine diced chicken, chopped bacon, shredded cheddar cheese, and ranch dressing until ingredients are well mixed.
02 - Lay a flour tortilla flat on a work surface. Evenly distribute one-fourth of the filling over half of the tortilla, then fold the tortilla in half to enclose the filling.
03 - Heat a large nonstick skillet over medium heat and lightly coat with cooking spray or melt a portion of the butter. Place the folded tortilla in the skillet and cook for 2-3 minutes per side, flipping once, until golden brown and cheese is melted.
04 - Transfer cooked quesadilla to a cutting board. Allow to cool slightly, then cut into wedges. Repeat process for remaining quesadillas, adding more butter or cooking spray as needed.