Cook the rice: combine the rice and broth in a small pot over medium heat. Bring to a boil, and reduce heat to low, simmering for 30 to 45 minutes. Set aside.
In a medium bowl, combine the apple, grapes, celery, and chickpeas.
Divide the rice and lettuce among 4 bowls. Top with the chickpea mixture and walnuts.
Make the dressing: whisk together the Greek yogurt, mustard, lemon zest, lemon juice, salt and pepper. Drizzle over the bowls.
Enjoy!