Preheat a grill to medium high. Combine the bell peppers, red onion, chile pepper, thyme sprigs and cherry tomatoes in a bowl; toss with 3 tablespoons olive oil and 1/2 teaspoon salt.
Lay out four 20-inch-long sheets of heavy-duty aluminum foil. Top each sheet with a pile of vegetables, then add 2 tablespoons vinegar to each.
Place a fish fillet on top of each pile of vegetables; drizzle each with 1/2 tablespoon olive oil and season generously with salt. Bring the two short ends of the foil together and fold twice to seal; fold in the sides to form a packet.
Grill the foil packets, moving them around as needed for even cooking, until the fish is cooked through, 10 to 12 minutes.