Soak wooden skewers in water for at least 30 minutes.

In a Zip-loc bag, combine olive oil, soy sauce, minced garlic, Worcestershire sauce, lemon juice, red wine vinegar, Dijon mustard, and black pepper.

Cut sirloin steak into 1-inch pieces and add them to the marinade-filled bag. Marinate for 3 to 6 hours in the refrigerator.

Wash and cut bell peppers, red onion, and zucchini into 1 1/4-inch chunks. Toss with olive oil, salt, and pepper.

Thread steak pieces and veggies onto soaked skewers alternately.

Grill kabobs on medium-high heat for 3-4 minutes on each side until cooked to medium rare to medium.