- 8 tablespoons 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
- 0 freshly ground pepper
- 4 (6-ounce) skin-on snapper fillets
- 1 bunch scallions
- Parsley leaves with tender stems (for serving)
- Prepare grill for medium-high heat; oil grate. Combine onion, vinegar, and 6 tablespoons oil in a small bowl; season with salt and pepper. Set marinade aside.
- Rub snapper all over with 1 tablespoon 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; if it sticks, grill another minute or two). Turn; grill until just cooked through, about 1 minute. Place skin side up in a baking dish.
- Pour reserved marinade over hot snapper and let sit at least 10 minutes (the longer it sits, the more intensely flavored it will be).
- Meanwhile, toss scallions on a baking sheet with remaining 1 tablespoon oil; season with salt and pepper. Grill, turning often, until lightly charred and wilted, about 2 minutes. Transfer to a cutting board. Let cool; coarsely chop.
- To serve, spoon marinade over snapper and top with scallions and parsley.
- Snapper can be marinated 2 hours ahead. Cover and chill.