Technically, Fajitas are said to be a "Tex-Mex" dish rather than Mexican cuisine. Originally, fajitas were made with steak however, folks enjoy many variations of fajitas these days. Fajitas are strips or pieces of meat/chicken/protein that are cooked quickly in a skillet with sliced onions and peppers. They are also served with with tortillas, which can be used to hold the ingredients for consumption. This recipe for fajita casserole takes the ingredients that are commonly used to make fajitas and baked them in a casserole dish rather than on a skillet.