In a large skillet, sauté onion in vegetable oil for about 10 minutes or until golden. Stir in mushrooms, oregano and garlic. Add salt and black pepper to taste. Sauté 5 more minutes. Add frozen peas and cook until peas are thawed. Stir in ginger. Cover and remove from heat.
Bring 3 quarts water to a boil in a large pot. Add bouillon cubes or instant soup mix to flavor the water. Add orzo and cook according to package instructions, stirring occasionally. Drain in a colander and return orzo to pot.
Add sautéed vegetables to pot and mix well. Cook over low heat, stirring constantly, until heated through.
Adjust seasoning. Sprinkle with Parmesan cheese before serving, if desired.
Note: Orzo, made from wheat, is available in Italian specialty shops and many grocery stores.