Heat oil in a frying pan or large skillet over medium heat.
Add chicken, onions and bell pepper into pan, sprinkle with taco seasoning, garlic salt, cumin, pepper and red pepper flakes, stir and cook until chicken is cooked and onions are translucent.
Pour diced green chilies into pan, stir until combined and continuing cooking for a few more minutes.
In another frying pan, melt 1 tablespoon of butter and place a tortilla into pan,
Add chicken mixture on one half of tortilla, add both types of cheese on top of chicken, fold tortilla over and add another tortilla to pan and repeat process.
Cook over medium heat until tortillas starts to brown, flip over and cook the other side.
Remove from pan, place on a plate.
Add the other tablespoon of butter to pan and repeat with the remaining tortillas and chicken mixture until all 8 quesadillas are made.
Cut into wedges right before serving.
Top with your favorite toppings like sour cream, green onions, cilantro and/or avocado, then enjoy!
*Can use Rotisserie chicken or shredded chicken