Preheat oven to 325 degrees
Spray a baking dish with the nonstick spray and place halibut in the dish. Add milk and cooking sherry. Sprinkle with salt, pepper, garlic powder, and the contents of one Lemon Tea Bag. Place onion and mushroom slices on top of fish. Again sprinkle with salt, pepper, garlic powder and the contents of one Lemon tea bag. Place lid over the mixture and cook for approximately 25 minutes. Check fish after 20 minutes making sure to not over cook.