Peppers and onions grill with skirt steak for fajitas.
Fajitas originated in Texas, and as such we should have the last word on how to make them. For instance, if we were to make the World's Biggest Fajita Taco, I'd suggest to the Guinness Book people that genuine South Texans be consulted about how fajitas are made (beef fajitas are made with skirt steak) and when they are cut (after the steaks are grilled).
But, as for the marinade, it seems just about any ol' ingredient will do. Soy sauce and Worcestershire Sauce seem to crop up in recipes created by real Texans, including respected cooks and restaurateurs. Glancing through several sources recently, I found some recipes called for herbs, such as basil, or spices, such as cumin. Some have garlic, some don't.
The first time I made fajitas, according to the recipe I was using, they were doused in a ton of Worcestershire Sauce. I'd had to special order the skirt steak to be shipped up from Phoenix, as no stores in Prescott, Ariz., as yet, were carrying this inexpensive cut back in the mid-1980s. I had to order a 40-pound box, and they cost, maybe, $1.29 a pound.
Forty pounds of skirt steak serves quite a few people, so it was a big party. My guests seemed to like this dish, unfamiliar to them at the time. But I thought my fajitas tasted awful. The second time I had them was at a restaurant in Flagstaff, Ariz. These, too, were laced with Worcestershire, and I thought, OK, I guess I just don't like fajitas.
Then, I visited my husband-to-be in San Antonio. He, as part of the his ploy to lure me permanently to the Alamo City, took me directly to the old Rosario's. If either Worcestershire sauce or soy sauce was in the marinade, it wasn't the main ingredient. I was hooked.
The upshot of all this is: San Antonio needs to have a fajita cook-off. I'd be interested to see how many cooks used basil in their marinade.
Recipe for SavorSA Fajitas