Heat gas or charcoal grill. In medium bowl, mix mushrooms, garlic, oil and vinegar.
Place mushroom mixture in grill basket (grill "wok"). Place basket on grill over medium heat. Cook 5 to 7 minutes, shaking basket or stirring once or twice, until mushrooms are tender.
Add tomatoes; cook and stir 1 minute longer or until tomatoes are hot. Pour into serving bowl. Sprinkle with parsley.