Preheat the oven to 400 degrees F.
Spread the chopped onions in the bottom of a large baking dish and drizzle with olive oil. Rub the steaks with the seasoned salt, pepper and garlic and place on top of the onions in a single layer. Drizzle the steaks with olive oil and balsamic vinegar. Pour the beer over the steaks and tuck the mushrooms and peppers around the steaks. Roast the steaks in the oven for 30 to 45 minutes.
This recipe was created by a contestant during a cooking competition. The Food Network Kitchens have not tested it for home use, therefore, we cannot make any representation as to the results.