Clean the mushrooms and remove the stems. Chop the stems finely.
In a mixing bowl, combine the chopped mushroom stems, breadcrumbs, Parmesan cheese, minced garlic, olive oil, and chopped parsley. Season with salt and pepper to taste.
Stuff each mushroom cap with the mixture and place them on a baking sheet.
Bake for 20 minutes or until the mushrooms are tender and the stuffing is golden brown.