In a bowl, mix the chopped Mexican-spiced chicken and ranch dressing.
Divide the chicken mixture evenly between the two flour tortillas, covering half the surface of each tortilla.
Sprinkle both pepper jack and cheddar cheese evenly over the chicken mixture on each tortilla.
Fold each tortilla in half and press down gently.
Heat a medium non-stick skillet over medium-high heat and lightly spray it with non-stick cooking spray.
Carefully place one quesadilla onto the hot skillet and cook until golden brown on both sides, about 2-3 minutes per side. Repeat this process with the remaining quesadilla.
Transfer the cooked quesadillas to a wire rack to cool slightly. If not serving immediately, let them fully cool on the wire rack to avoid sogginess.
Cut each quesadilla into 4 wedges and serve with pico de gallo on the side.
Let the cooked quesadillas cool completely on a wire rack. Slice into wedges and pack into meal prep containers. Store in the refrigerator for up to 3 days.
To reheat, place a cast iron or non-stick skillet over medium heat and cook the quesadilla on both sides until the crust is crispy and the filling is heated through. Alternatively, microwave each quesadilla at 30-second intervals until heated through.