Wash large mushrooms, pat dry, and place in large bowl or baking dish.
If the stems in the middle are large, cut it.
Place all other ingredients in a small bowl and whisk together. Drizzle over the mushrooms.
Cover and place in the refrigerator to marinate for at least 30 minutes or overnight.
When ready to cook preheat oven to 350°F.
Place the marinated mushrooms in a baking pan lined with parchment paper to prevent sticking and to make for easy cleanup. Or you can use non-stick silicone baking mats.
Bake in the oven for approximately 25-30 minutes.
Mushrooms release their water while baking so, when they are done, drain the water or use a paper towel to blot away the excess liquid.
If grilling, use low heat. Allow to cook for approximately 30 minutes.
Serve on whole-grain buns with grilled onions, lettuce, and favorite toppings.