Preheat your oven to 375°F (190°C).
In a mixing bowl, combine the softened cream cheese, cheddar cheese, crumbled bacon, green onions, ranch seasoning, garlic powder, and black pepper. Mix until well combined.
Spoon the cheese mixture into each mushroom cap, filling them generously.
If using breadcrumbs, sprinkle them on top of the stuffed mushrooms for added crunch.
Place the stuffed mushrooms on a baking sheet lined with parchment paper. Drizzle with olive oil.
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 before serving.