1. Heat the oven to 450°. In a large roasting pan, combine the red and green bell peppers, the corn, 1 tablespoon of the oil, and 1/4 teaspoon each of the salt, pepper, and thyme. Roast in the oven until the corn and peppers start to brown, about 12 minutes, stirring twice.
2. Rub the remaining tablespoon oil over both sides of the fish. Sprinkle the fish with the remaining 1/4 teaspoon each salt, pepper, and thyme. Remove the roasting pan from the oven and push the corn-and-pepper mixture to the sides of the pan. Put the fish in the center of the pan, skin-side down, and cook until just done, about 15 minutes for 1-inch-thick fillets. Serve the fish with the corn and peppers.
Fish Alternatives: Other moderately firm fish to roast here include tilefish, sea bass, and cod. If the fillets are skinned, coat them with a bit of oil before adding to the pan.
Test-Kitchen Tip: If using frozen corn kernels, let them defrost if you can; it only takes a few minutes. Measure the corn first thing and it will be defrosted by the time you're ready for it. Pat the corn dry with a paper towel after defrosting so that the excess moisture won't get in the way during cooking and make browning impossible.
Wine Recommendation: Any number of light white wines will go nicely with this. Try a chardonnay from France, such as a Mâcon-Villages or one of the newer-styled chardonnays from the Pays d'Oc region.