In a large skillet or wok, heat oil over medium heat until hot. Add onion, cook and stir until tender, about 3 minutes. Add garlic, ginger, chili pepper, snow peas, bell pepper and mushrooms (except oyster mushrooms if used). Cook and stir until moisture evaporates, 5 to 7 minutes. Add oyster mushrooms (if used). Cook until barely softened, about 2 minutes. Stir in oyster-flavored sauce and wine.