In a large skillet heat oil over medium-high heat. Add mushroom, onion, and garlic. Cook and stir for 4 to 5 minutes or until mushroom is tender. Add the wine and if using, dried herb. Bring to boiling; reduce heat. Simmer, covered, for 5 minutes to blend flavors. Stir in tomatoes and if using, fresh oregano; heat through. Remove from heat; cover and keep warm.
Meanwhile, for polenta, in a small bowl stir together 1/2 cup of the water and the cornmeal; set aside. In a small saucepan bring the remaining 1/2 cup water, the margarine, and salt just to boiling. Slowly add the cornmeal mixture, stirring constantly. Reduce heat to low. Cook and stir about 10 minutes or until polenta is thick. Stir in cheese.
To serve, divide the polenta between 2 shallow pasta bowls or soup bowls. Top with the mushroom mixture. If desired, garnish with additional fresh oregano.