Preheat your oven to 375°F (190°C).
In a skillet over medium heat, cook the Italian sausage until browned, breaking it apart with a wooden spoon, about 5-7 minutes. Drain excess fat if necessary.
In a mixing bowl, combine the cooked sausage, cream cheese, Parmesan cheese, breadcrumbs, garlic, oregano, salt, and pepper. Mix until well combined.
Stuff each mushroom cap generously with the sausage mixture, pressing down slightly to pack it in.
Arrange the stuffed mushrooms on a baking sheet lined with parchment paper.
Bake in the preheated oven for 20-25 minutes, or until the mushrooms are tender and the tops are golden brown.
Remove from the oven and let cool for a few minutes. Garnish with fresh parsley before serving.