Preheat oven to 400. In a 9-by-13-inch baking dish, combine bulgur, onion, butter, garlic, coriander, and 1 1/2 cups water. Season generously with salt and pepper; mix to combine, and spread evenly in dish.
Season each fillet with salt and pepper; roll up and place on top of bulgur mixture. Season rolls again with salt and pepper. Tightly cover dish with aluminum foil, and bake until bulgur is tender and fish is opaque throughout, 25 to 35 minutes. Serve fish with bulgur pilaf; garnish with lemon wedges and cilantro or parsley, if desired.