Heat oven to 350 degrees F.
Sprinkle salt and pepper evenly over pork, place in a 9x13-inch baking pan and set aside.
Melt butter with garlic in a medium saucepan, add mushrooms, bring to a boil, reduce heat, simmer, uncovered 5 to 6 minutes or until just tender, stirring frequently. Add vinegar to mushroom mixture, spoon over pork, placing some of the mushrooms on top of the pork. Roast 20-27 minutes, uncovered or until internal temperature reaches 145 degrees Fahrenheit, followed by a 3-minute rest time. May baste occasionally, if desired. Makes 1 cup mushroom sauce total.
Serves 6 to 8