"True" Tabbouleh is based on a cracked bulgur wheat and not couscous as stated in the recipe in the May 2013 issue. Couscous is a variation. I mention this because the description on the recipe states that it was a recipe for "true" tabbouleh. Although substituting couscous makes a good alternative, it is not traditional.
If using couscous, the Israeli Couscous or one of the other larger varieties makes a wonderful salad.