DO-AHEAD TIP: If using bamboo skewers, soak them in water for 30 minutes to prevent burning.
Preheat outdoor grill to MEDIUM-HIGH. Alternately thread bell peppers, onion and beef onto the skewers.
In a small bowl, mix remaining ingredients (garlic through olive oil); brush a thick coat of this seasoning mixture over the kabobs and grill for 2 to 4 minutes per side or until cooked to the desired level of doneness.