Place couscous in large bowl. Pour 1 cup boiling water over couscous and let stand. In saucepan, bring vegetable stock to boil, add thyme and vinegar. Boil to reduce to 0.75 cups. Add peas and corn to liquid and turn off heat. Toss tomatoes, scallions, and basil into couscous. Add liquid to couscous and mix well.
Cover and refrigerate 2 hours before serving. To serve, top a romaine leaf with couscous mixture. Makes 6 servings
Per serving:197 calories, 2 grams fat