Heat oven to 350°F.
Twist mushroom stems to remove from mushroom caps; reserve caps.
Finely chop enough stems to measure about ½ cup; discard remaining stems.
In medium bowl, mix chopped mushroom stems and remaining ingredients until well blended.
Spoon into mushroom caps, mounding slightly.
Place in ungreased 15x10x1-inch pan.
Bake 15 to 20 minutes or until hot.
Serve warm.