Preheat oven to 450ºF. Brush a half-sheet pan with 1½ Tablespoons of melted butter.
Place 6 flour tortillas around the edges of the sheet pan, with the tortillas hanging halfway over the edge of the pan, leaving a gap in the center. Place 1 tortilla in the bottom center gap.
In a large bowl, stir together cooked chicken, bacon, sour cream, ranch seasoning, ranch dressing, and shredded cheddar cheese.
Evenly spread the chicken mixture over the tortillas.
Place the last tortilla in the center of the mixture. Carefully begin folding the tortillas that are hanging over the edge of the pan, towards the middle. Brush with remaining melted butter. Place a second sheet pan on top of the folded tortillas and press down a bit.
Transfer the stacked baking sheets to the oven and bake for 20 minutes. Remove the top baking sheet and bake for 15 more minutes, or until the tortillas are lightly golden.
Remove the sheet pan from the oven and allow the quesadilla to slightly cool before cutting it into servings.
