Brush grill lightly with olive oil, or use a grill spray. Turn on grill , and preheat on medium -high heat for about 15 minutes. Remove steaks from the bag or container, and shake off excess. Lightly sprinkle the garlic salt onto both sides of the meat. Now you're ready to grill.
Place on grill, and cook for about 4- 5 minutes per side to reach desired doneness. Remove steak from grill, transfer to a cutting board place foil over top. Let rest 5 minutes until veggies are done sautéing.
Meanwhile as the steak is grilling, it's time to sauté the veggies. In a large pan, heat 1 teaspoon olive oil, and the 2 tablespoons marinade. Add the bell peppers first, and sauté for about 3 minutes so they start to soften, then add the onions and continue to cook for an additional 5-7 minutes until all veggies are soft.
Now slice meat against grain, and again into 1/2" pieces. (Remember you can slice this thin as well, but the kids like it cut this way.)
Here's 3 options for warming the tortillas, depending on what you like. 1. For soft tortillas: wrap 4-5 tortillas tightly in sheets of foil for 2-3 minutes on the grill. 2. For soft, but quick tortillas: place in damp paper towels in microwave and heat 30-40 seconds until warmed. 3. If you like them crisper, add a drop of olive oil to the sauté pan and let this get hot, place tortillas in the pan letting them brown on both sides. (this is our favorite)
To assemble the fajita, top warm tortillas with grilled steak, veggies and desired toppings. (guacamole, sour cream or crema fresca, cilantro, spritz of lime, Cotija or cheddar cheese)