To make the marinade, place ⅓ cup olive oil, orange juice, lime juice, soy sauce, vinegar, garlic, cumin, chili powder, ground coriander, salt, and pepper in a medium bowl.
Whisk to combine the marinade. Remove ¼ cup of the marinade, cover, and refrigerate for use later.
Place the steak(s) in a casserole dish.
Coat the steak in the marinade, cover the casserole dish with plastic wrap, and refrigerate for 4 hours.
Once marinated, remove the steak from the casserole dish, letting any excess marinade drip off.
Heat 1 tablespoon of olive oil in a large cast iron skillet over high heat.
Once hot, working in batches if necessary, place the steak in the skillet, and sear for 3 to 4 minutes per side until deeply browned (for medium-rare).
Remove the steak from the skillet and set aside to rest on a clean plate.
Add the remaining 1 tablespoon of olive oil to the skillet and reduce the heat to medium.
Add the bell peppers and onion to the skillet, stir to combine, and saute for 5 to 6 minutes or until tender.
Deglaze the skillet with the reserved marinade to kickstart the sizzle.
Slice the steak into strips and return to the skillet.
Immediately transfer the sizzling skillet to your serving surface (making sure to place the skillet on a trivet).
Serve your fajita steak and veggies with flour tortillas, cheddar cheese, salsa, sour cream, guacamole, and fresh cilantro.