4 SERVINGS
The tangy, super-acidic dressing used here- thats the escabeche part- is great for adding brightness to other quick- grilled meats (like skirt steak), too.
8 tbsp olive oil,divided, plus more for grill
1/2 small red onion,thinly sliced
1/4 cup white wine vinegar
Kosher salt,freshly ground pepper
4 6-oz skin on snapper fillets
1 bunch scallions, halved if large
2 tbsp parsley leaves with tender stems
Prepare grill for medium high heat; oil grate. Combine onion,vinegar, and 6 tbsp in a small bowl; season with salt and pepper. Set marinade aside.
Rub snapper fillets all over with 1 tbsp oil total; season with salt and pepper. Grill, skin side down, until lightly charred and almost cooked through, 4-6 minutes (skin should release easily from grill when ready; if it sticks, grill for another minute or two). Turn fillets and grill until just cooked through, 1 minute. Place fish, skin side up, in a baking dish.
Pour reserved marinade over hot fish and let sit at least 10 minutes (the longer it sits, the more intensely flavored it will be).
Meanwhile, toss scallions on a rimmed baking sheet with remaining 1 tbsp oil; season with salt and pepper. Grill scallions, turning often, until lightly charred and wilted, about 3 minutes. Transfer to a cutting board; let coal, then coarsely chop.
Serve snapper with marinade and vegetables spooned over and topped with scallions and parsley just before serving.
DO AHEAD:
Snapper can be marinated 2 hours ahead. Cover and chill.