Prepare the Marinade: In a bowl, combine olive oil, soy sauce, balsamic vinegar, garlic powder, oregano, smoked paprika, black pepper, and salt. Stir well. Add the beef cubes to the marinade, and toss to coat evenly. Let the beef marinate for at least 15 minutes, or up to 2 hours in the fridge for extra flavor.
Prepare the Veggies: While the beef is marinating, chop the bell peppers, onion, and zucchini into chunks that are large enough to skewer but small enough to cook evenly.
Assemble the Kabobs: Thread the marinated beef cubes and vegetables onto the skewers, alternating between the meat and veggies. Leave a little space between each piece for even cooking.
Preheat the Air Fryer: Preheat your air fryer to 400°F (200°C) for about 3-5 minutes.
Cook the Kabobs: Place the assembled skewers into the air fryer basket in a single layer. You may need to cook the kabobs in batches depending on the size of your air fryer. Cook for 12-15 minutes, turning halfway through, until the beef is cooked to your desired level of doneness and the vegetables are tender.
Serve and Enjoy: Once the kabobs are done, remove them from the air fryer and let them rest for a couple of minutes before serving. Enjoy your healthy, crispy beef kabobs with your favorite side dishes!