Combine all ingredients in a heavy duty sealable freezer bag and freeze. (Or store in the refrigerator overnight).
When desired, remove from freezer and thaw in the fridge or a sink full of cold water.
Grill for 10-15 minutes or until medium (pink in the center).
Cut fajitas AGAINST THE GRAIN and serve with warmed tortillas, shredded cheese, lettuce, pico de gallo (#159078), sour cream, guacamole or your favorite toppings.
To cut fajitas against the grain, lay out on cutting board horizontally. The grain is running vertically. Cut the steak vertically into managable sized slabs and then slice horizontally (opposite the grain). The fajitas will be tender and soft.