1. Preheat oven to 350 degrees Fahrenheit.
2. Rinse steaks and pat dry; place them in a roasting pan. Rub steaks with minced garlic. Season with salt and pepper and sprinkle with onion soup mix. Bake tightly covered for two hours.
3. In a skillet, heat oil over medium heat. Sauté onions and mushrooms until soft.
4. In a separate bowl, combine steak sauce and white wine.
5. Remove steaks from oven, top with onion mushroom mixture, and pour sauce over steaks. Lower oven to 250 degrees Fahrenheit. Cover tightly and bake for an additional 50 minutes.