Chop the steak into 2-inch cubes then transfer it to a mixing bowl along with the marinade ingredients. Give everything a stir until the chunks of steak are coated in marinade. Cover the bowl with plastic wrap. Note: you can also add everything to a large resealable plastic bag. Seal bag and shake everything around. Refrigerate marinated steak for at least 10 minutes, up to 12 hours.
If you’re using a charcoal grill, be sure to get the coals going at least 20 minutes before grilling. If you’re using wooden skewers, soak the skewers in water (be sure they’re submerged as best as possible) for ideally 20 minutes prior to using them. This will help prevent them from igniting easily over the open flame of the grill.
When you’re ready to make the skewers, chop the bell peppers and onion and toss the vegetables in a large bowl with avocado oil and liquid aminos (or soy sauce).
Thread the steak cubes and vegetables onto the skewers until all of the marinated meat and veggies are used. This should make 6 to 8 large skewers, depending on the length of your skewers.
If using a gas grill, preheat the grill to a high heat, or set it for 500 degrees Fahrenheit.
Place kabobs over direct heat (over an open flame) and grill kabobs for 8 to 10 minutes, flipping once or twice, or until the meat reaches your desired level of doneness. If the grill is very hot, flip skewers every 2-3 minutes to avoid burning. The exact grill time is up to your personal preference and how you like your meat done.
Transfer the cooked BBQ steak kabobs to a serving platter, baking sheet, or large plate. Allow the meat to rest for 5 minutes before serving.