To prepare the fish, heat the oven to 400°. Put six 12-inch squares of aluminum foil on a work surface and rub liberally with butter.
Put a few slices of onion, lemon, and a sprig of thyme on the center of each square of foil. Place the each fish fillet over the onion/lemon/herb. Sprinkle the fillets with salt the pepper. Top with slices of onion and lemon. Gather the foil around the fish and drizzle the fish with the wine and oil. Fold the edges of the foil to make a sealed package. Put the foil packages on a baking sheet.
Bake the fish until just done, about 12 minutes. Open the foil packages and transfer the fillets with their vegetable topping to plates. Pour the juices over the top.
To make the roasted veg, preheat oven to 400 degrees F.
Cover a baking sheet with parchment paper. Place vegetables on the parchment paper, drizzle olive oil over the vegetables and sprinkle with salt, pepper and thyme. Toss to coat and place in oven. Roast 10-15 minutes, or until desired doneness. Serve with fish and enjoy!