Cut steak into 1-inch cubes. or rinse chicken, pat dry and cut into 1-inch pieces. Put steak and/or chicken in a plastic bag set in a shallow dish.
For marinade; In a saucepan, mix the barbecue sauce, water, garlic, dried onion, sugar, steak sauce, vinegar, Worcestershire, oil, and salt. Bring to just boiling. Cool. Pour over steak or chicken; seal bag. Marinate in refrigerator for 6 to 8 hours or overnight.
In a saucepan, cook onions, covered, in small amount of boiling water 3 minutes. Add mushrooms; cook 1 minutes. Drain. Thread vegetables onto skewers with zucchini and pepper.
Drain meat, reserving marinade; thread meat onto skewers. Cook on rack of uncovered grill over medium heat 12 to 14 minutes or until done, turning halfway through. In saucepan, heat marinade until bubbly.
Grill vegetables over medium heat for 5 to 10 minutes, turning occasionally; brush with heated marinade.
Serve immediately with warm marinade. Serves 4 to 5 servings.