Combine the tomato, cheese, 1/2 teaspoon oil, rosemary, pepper, and garlic in a small bowl.
Remove brown gills from the undersides of mushroom caps using a spoon, and discard gills. Remove stems; discard. Combine 1/2 teaspoon oil, juice, and soy sauce in a small bowl; brush over both sides of mushroom caps. Place the mushroom caps, stem sides down, on grill rack coated with cooking spray, and grill for 5 minutes on each side or until soft.
Spoon 1/4 cup tomato mixture into each mushroom cap. Cover and grill 3 minutes or until cheese is melted. Sprinkle with parsley.
Notes: Since the garlic isn't really cooked, the mushrooms have a strong garlic flavor. Grill the mushrooms stem sides down first, so that when they're turned they'll be in the right position to be filled. If you want to plan ahead, remove the gills and stems from the mushrooms and combine the filling, then cover and chill until ready to grill.