1. Preheat oven to 350ºF. Place quinoa in base of an ovenproof baking dish. In a saucepan, bring broth to a boil over medium-high heat; pour over quinoa. Cover and bake for 10 minutes. Stir quinoa, top with beans and chicken and sprinkle with salt and pepper. Cover dish tightly with foil and bake until quinoa is tender and chicken is cooked through, 25 to 30 minutes.
2. Make gremolata: In a bowl, mix parsley, mint, lemon zest and juice, olives and oil until well combined. Divide chicken and quinoa among 4 plates. Spoon gremolata over and serve.