1. Bring chicken broth to a boil in a saucepan; add 1 cup couscous, cover, and remove from heat. Let stand 10 minutes.
2. Toss together couscous, beans, and next 4 ingredients in a large bowl. Drizzle with Mint Vinaigrette, gently tossing to coat. Cover and chill until ready to serve. Serve over shredded lettuce, and, if desired, sprinkle with feta just before serving.