In a bowl, combine the olive oil, garlic, rosemary, thyme, salt, and pepper. Mix well.
Add the beef cubes to the marinade and toss to coat. Let marinate for at least 15 minutes.
Preheat grill to medium heat.
Thread the marinated beef, zucchini, bell peppers, and onion onto skewers.
Grill the kabobs for about 10 minutes, turning occasionally, until the beef is cooked to your desired level of doneness.
Serve the kabobs hot and enjoy!