Lay down one tortilla in the skillet and sprinkle with 1/2 cup mozzarella cheese. Top the mozzarella with a layer of 1/2 cup chicken, 1/4 cup red onion, and 2 tablespoons cilantro. Sprinkle 1/4 cup cheddar cheese on the chicken and drizzle with 1/4 cup BBQ sauce.
Lay a second tortilla on top and press down.
Allow the bottom tortilla to brown and then flip the quesadilla over to cook the other side.
Once the cheese is melted and tortillas are toasty, remove from skillet to a cutting board.
Cut quesadilla into 4 pieces. Repeat with remaining tortillas and ingredients.
Serve warm with more BBQ sauce for dipping. Garnish with cilantro if desired.
You can adjust the amount of chicken, red onion, cilantro, and bbq sauce in your quesdaillas to your preference.