Heat a skillet over medium heat and add 1 tbsp oil. Add chicken pieces and sprinkle with taco seasoning. Cook for 4 minutes, stirring occasionally.

Add diced bell pepper and onion to the skillet. Cook for an additional 5 minutes until the chicken is fully cooked and the vegetables have softened.

Wipe the skillet clean if needed, then add a small amount of butter or oil. Heat over medium heat and place one tortilla flat on the skillet.

Sprinkle some Mexican cheese on one half of the tortilla, add a portion of the chicken and vegetable mixture, and top with more cheese. Fold for a half-moon shape.

Cook for a few minutes until golden brown and crispy. Flip and cook the other side until golden and cheese melts. Repeat with remaining tortillas.

Remove quesadillas from the skillet and serve immediately while warm and gooey.