In medium saucepan, combine all couscous ingredients except couscous. Bring to a boil. Remove from heat; stir in couscous. Cover; let stand while broiling kabobs.
Meanwhile, spray broiler pan with nonstick cooking spray. Thread mushrooms, zucchini, bell pepper and onion onto four 12-inch metal skewers. Place on sprayed pan.
In small bowl, combine oil, vinegar and garlic salt; mix well. Brush over kabobs.
Broil 4 to 6 inches from heat for 10 to 12 minutes or until vegetables are crisp-tender, turning once halfway through cooking. Fluff couscous with fork; serve with kabobs.