Add all marinade ingredients to a bowl and stir. Pour the marinade into a ziploc bag and add the steak. Marinate for at least 4 hours.
Heat a grill to medium high heat. Add the steak and cook 4 minutes per side. Let the steak rest on a cutting board for several minutes before cutting.
While the steak is resting, heat the Garlic Olive Oil in a cast iron skillet on medium-high heat. Add the bell pepper slices and jalapeno pepper, stirring frequently for 4-5 minutes. Add the onion slices and cook for another 2-3 minutes.
Slice the steak into long, thin, diagonal strips, then toss back into the peppers and onions. Remove from heat.
Distribute the steak and peppers between the 6 tortillas, and top with jack cheese, cilantro and sliced avocado. Roll and enjoy!
Prep: 15 minutes
Marinate: 4 hours
Cook: 15 minutes
Makes: 6 Fajitas