Heat 2 tablespoons olive oil on medium-high in a large skillet. When the oil is very hot, add mushrooms. Arrange the mushrooms in the skillet so they are in a single layer. Cook, without stirring, until mushrooms are golden brown. Reduce heat to medium-low and add salt, pepper, and red onion and continue to cook. Stir often, until mushrooms are golden brown on all sides.
Add thyme, and garlic, continue to cook, making sure mushrooms are coated in thyme and garlic. Remove from heat, drain and reserve any excess oil and set mushrooms aside.
In a large mixing bowl, toss barley, cilantro, parsley, lemon juice, 1/3 cup of Parmesan, and any oil drained off the mushrooms, mix well. Add the reserved mushrooms and toss again, just to combine. Spoon into serving dishes and top with remaining Parmesan. Enjoy!
OPTION: 2 cups of cooked and cooled brown rice can be substituted for barley. Follow directions as indicated.