GRILL DIRECTIONS: In small bowl, combine all marinade ingredients; beat with wire whisk until well blended. Add turkey cubes; toss to coat. Let stand at room temperature to marinate while preparing vegetables.
Heat grill. Cut onion into 6 wedges; cut bell pepper into 6 pieces. To prepare kabobs, drain turkey, reserving marinade. Alternately thread 3 pieces turkey, 3 mushrooms, 3 tomatoes, 3 onion wedges and 3 bell pepper pieces on each of two 12 to 14-inch metal skewers.
When ready to grill, place kabobs on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Brush kabobs with reserved marinade; discard remaining marinade. Cook 10 to 15 minutes or until turkey is no longer pink and vegetables are crisp-tender, turning occasionally.
Meanwhile, in medium saucepan, combine water, margarine and 1/4 teaspoon salt. Bring to a boil. Stir in couscous. Remove from heat. Cover; let stand 5 minutes. Fluff couscous with fork before serving. Serve kabobs over couscous.