Preheat oven to 400 degrees F. Spray a large baking sheet with nonstick cooking spray; set aside.

Wash and dry mushrooms and place in a large mixing bowl. In a separate bowl, whisk together melted butter, balsamic, soy sauce, brown sugar, garlic, salt and pepper. Pour mixture over mushrooms and toss until evenly coated.

Spread mushrooms in an even layer on prepared baking sheet. Cook for 20 minutes, stirring halfway through.

Remove from oven and toss mushrooms in any remaining sauce and garnish with parsley.