In a large saucepan, bring the water and salt to a boil over high heat. Add the bulgur or rice and vegetables and stir to combine. When the mixture returns to a boil, reduce the heat to low, then cover the pan and simmer for 15 minutes. Set aside off heat, still covered, for 5 minutes.
Using a fork, scrape the mixture into a large bowl. Add the lemon juice, walnuts, onions and parsley and combine by stirring and tossing with a fork. Season with pepper to taste. Spread the lettuce around the rim of a large platter.
To make the dressing, stir together the yogurt, lemon juice and parsley in a small bowl.
Mound the salad in the center of the lettuce and spoon some of the dressing over the salad. Pass the remaining dressing at the table.