In a large glass bowl, combine all the ingredients except the couscous and walnuts. Mix well and let stand at room temperature for at least one hour.

Meanwhile, prepare the couscous according to package directions. Turn cooked couscous out into 13 X 9 -inch baking dish. Fluff with a fork. Cool 10 minutes.

In a large nonstick skillet, heat walnuts over medium-high heat. Cook and stir until golden and fragrant.

Combine cooled couscous with dressing ingredients and sprinkle with walnuts.