In a shallow dish, combine 2 tablespoons EVOO, the parsley, lemon juice and peel, lime juice and peel, orange peel, hot sauce and thyme; season with salt and pepper. Add the fish and let marinate for 15 minutes.
Meanwhile, preheat a grill or grill pan to medium. In a medium saucepan, heat the remaining 1 tablespoon EVOO , 1 turn of the pan, over medium heat. Add the bell pepper and scallions, season with salt and pepper and cook until softened, 3 to 4 minutes. Add the chicken broth and bring to a boil over high heat. Stir in the couscous, cover and keep warm.
Grill the fish until cooked through, about 3 minutes on each side.
Fluff the couscous, then mix in the chopped orange. Serve with the fish.