In a saucepan, bring water to a boil. Stir in couscous; cover and remove from the heat. Let stand for 5 minutes.
In a small skillet, saute the carrot and onion in butter for 3-4 minutes or until crisp-tender. Add zucchini and green onion; saute 2-3 minutes longer or until tender. Sprinkle with salt and pepper. Fluff couscous with a fork; add vegetable mixture and toss to combine.