Using a glass baking dish, whisk together all of the ingredients except for chicken breasts. Add chicken breasts, turning several times to coat with marinade. Cover and refrigerate overnight.

The next day, preheat grill to medium heat.

Remove chicken breasts from marinade and grill 10-12 minutes, or until fully cooked. (Note: Discard any excess marinade.)

Let chicken rest for 5 minutes before cutting into ½” cubes.

Reduce heat on grill to medium-low. (Note: These quesadillas can also be made in a large skillet on the stovetop. You’ll likely need to make them in 2 rounds unless you use multiple skillets.)

Brush one side of the quesadillas with the melted butter. Spread ~3 Tbsp of ranch dressing evenly on top of each tortilla.

Divide bacon, chopped chicken and cheese evenly between quesadillas. (Note: Layer the fillings on one half of each quesadilla so that they’re easier to fold. Also make sure to put cheese on bottom and top of fillings to help hold quesadillas together as they cook.)

Grill quesadillas for 2-3 minutes per side, or until cheese has fully melted. Watch them closely as they can burn quickly on the grill!

Slice quesadillas into wedges and serve with diced tomatoes, sour cream, guacamole and additional ranch dressing.