This was taken from Spur of the Moment Cook by Perla Meyers (William and Morrow Co.). Some minor changes were made to the original recipe.
Preheat oven to 400°. Combine the vinegar, salt, and pepper in a large bowl. Add the oil in a stream, whisking until well blended. Add the garlic, rosemary and mushrooms and toss to coat well. Transfer to a heavy baking sheet (or jelly roll pan) and roast for 15 minutes or until the mushrooms are tender and lightly browned, turning once during cooking. Serve immediately. 4 servings.