Heat oven to 400° F.
Heat 1 tablespoon of the oil in a large ovenproof skillet over medium heat. Add the sausage and cook, turning once, until it starts to brown, 5 minutes. Add the onions, 1/2 teaspoon salt, and 1/2 teaspoon pepper and cook, stirring, for 4 minutes. Add the bell peppers and garlic and cook until they are just soft, about 4 minutes. Stir in the wine and thyme.
Transfer the skillet to oven. Roast until the sausage is cooked through, about 15 minutes.
Heat the remaining oil in a large nonstick skillet over medium-high heat. Cook the polenta in batches, turning once, until golden brown.
Place the polenta on a platter. Spoon the sausage, vegetables, and pan juices over the top. Serve with the crusty bread, if desired.
Tip: Logs of ready-to-eat polenta are a cook's secret weapon. Sold in the international section of the supermarket, the corn-meal mixture can be sliced into rounds to bake, broil, or sear. Use polenta as a base for fish, chicken, or hors d'oeuvres.