Preheat oven to 400 degrees F. Line a rimmed baking sheet with parchment paper or foil.
Place the mushrooms on sheet pan.
In a medium mixing bowl, combine cream cheese, cooked bacon, cheddar cheese, jalapenos, garlic powder, salt, and pepper. Stir well.
Spoon 1 tablespoon of filling into each mushroom cap (this amount will vary depending on the size of your mushrooms).
Bake for 20-25 minutes, until mushrooms are hot and cheese is melted.
Carefully remove mushrooms from the oven and let them rest for 5 minutes before plating.
Garnish with green onions and more cheddar cheese. Serve immediately.