Preheat the oven to 375 degrees F.
Place the oil in a large skillet and set over medium to medium-high heat. Add the sausages and quickly brown them (do not cook them through). Set the sausages in a 9 x 13-inch casserole.
Add the onion, bell peppers and garlic to the skillet and cook 3-4 minutes. Spoon this mixture over the sausages. Pour in the stock and roast the sausages, uncovered, for 30 minutes, or until cooked through. Sprinkle the sausages with parsley or oregano and serve.