Season the chicken with taco seasoning on both sides.
In a skillet, heat oil over medium-high heat. Cook the chicken on both sides until cooked through, 4-5 minutes per side.
Transfer the chicken onto a cutting board. Let cool and then cut into small, bite-sized pieces.
In a medium bowl, combine chicken, cheese, corn, scallions, and cilantro.
Take ¼ of chicken mixture and spread over half of a tortilla, leaving about ½-inch border at edge. Fold the tortilla over filling, pressing firmly to seal. Continue with the remaining tortillas and filling.
Melt 2 tbsp of butter in 12-inch non-stick skillet over medium heat.
Place 2 quesadillas in the skillet and cook, firmly pressing with a flat spatula, until tortillas are golden brown and cheese is melted, about 2 minutes per side.
Transfer to a cutting board, and repeat with the remaining butter and 2 quesadillas.
Cut into wedges and serve with salsa, sour cream and/or guacamole, optional.