In a small bowl or blender, combine the avocado oil, lime juice, garlic, and fajita seasoning.
Cut the steak think against the grain. Place the steak in one zip-top bag or shallow dish and the vegetables in another. Pour half of the marinade over the steak and the other half over the vegetable. Marinate for at least 1 hour and up to 4 hours.
Line your air fryer with an air fryer liner or foil.
Remove the vegetables from the marinade and drain. Set your air fryer to 400 degrees. Place the vegetables in the air fryer and cook for 13 minutes. Remove from the air fryer.
Remove the steak from the marinade and drain. Place the steak in the air fryer basket, and cook for another 7 to 10 minutes, until the steak is 130 degrees F for medium-rare.