Clean mushrooms with damp paper towels. Remove stems. Set mushroom caps aside. Finely chop stems, and set aside.
Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Add mushroom caps; saute 5 minutes. Remove from skillet, and drain on paper towels. Coat skillet with cooking spray, and add reserved mushroom stems and green onions; saute over medium heat 3 minutes or until tender. Remove from heat. Stir in breadcrumbs, Parmesan cheese, and salt. Set aside.
Crumble goat cheese evenly into mushroom caps. Spoon breadcrumb mixture evenly into mushroom caps over goat cheese, and sprinkle evenly with pepper. Arrange mushrooms on rack of a broiler pan coated with cooking spray. Broil 5 1/2 inches from heat (with electric oven door partially opened) 2 to 3 minutes or until lightly browned.