In a 4-quart Dutch oven cook onion and garlic in hot oil over medium heat until tender. Add carrots, sweet potato, turmeric, cumin, and salt. Add water. Bring to boiling; reduce heat. Simmer, covered, for 5 minutes, stirring occasionally. Add yellow squash, zucchini, and sweet pepper. Cover and cook about 5 minutes more or until vegetables are tender. Stir in chopped tomato.
Meanwhile, prepare couscous according to package directions adding optional salt. Transfer couscous to a very large bowl. Add vegetable mixture; stir gently to combine. Stir in mint. Serve immediately. Makes 10 servings