Preheat oven to 350°. Lightly grease a 6 cup ovenproof casserole dish. Add cornmeal, water, oil and salt, and stir with a fork until blended (the mixture will separate, but will come together near the end of the cooking time). Bake, uncovered, for 30 minutes. Remove dish from oven, and stir with fork; smooth polenta with an offset spatula or knife, and return to oven for approximately 5 minutes, or until polenta is firm. Let cool completely prior to cutting into rounds.
This recipe from The Slow Mediterranean Kitchen (Paula Wolfert, 2003) has made it so easy to fix polenta that it now appears more frequently on our table. We realized the technique should work for stone-ground grits, and happily that is true. In either case, the recipe can be doubled. In addition to using a larger casserole dish, the cooking time will need to be increased by approximately 30 minutes. If you desire a less firm finished product, increase the amount of water.