Discard stems from mushrooms; scrape out gills with small spoon. Brush mushrooms with oil; grill 2 min. on each side or just until mushrooms start to soften. Place, rounded-sides down, on foil-covered baking sheet. Dab insides of caps with paper towels to remove excess moisture.
Fill caps with remaining ingredients.
Grill 6 to 8 min. or until filling is heated through. Serve warm.
