― I used diced lean beef steak.First I cooked my onions and peppers, then added the steak. Cooking on a low heat, I added Old El Paso BBQ Fajita Mix. I let the beef cook as much as I wanted it to, then turned off the heat, covered with tin foil and let rest for 10 minutes. We then added out choice of extras, garlic mayo and cheese, nom, and wrapped up in flour tortillas. .