Preheat the oven to 400°F (200°C). Line a large baking sheet with parchment paper for easy cleanup.
Slice each mini pepper in half lengthwise. Remove the seeds and white membranes. Place the pepper halves in a large bowl, add the olive oil, and toss to coat.
Arrange the peppers cut-side up on the prepared baking sheet. Bake for 6 to 8 minutes, just until they begin to soften.
While the peppers are in the oven, cook the ground sausage in a large skillet over medium-high heat. Break it apart with a spoon until it is browned and fully cooked to an internal temperature of 160°F (71°C). Drain off any excess grease.
In a medium bowl, combine the room temperature cream cheese, 1/4 cup of the shredded cheese, garlic powder, dried parsley, salt, and pepper. Mix until smooth.
Add the cooked sausage to the cream cheese mixture and stir until everything is well combined.
Remove the peppers from the oven. Carefully spoon the sausage and cheese filling into each pepper half. It's okay to mound the filling.
Sprinkle the remaining 1/4 cup of shredded cheese over the top of the stuffed peppers.
Return the baking sheet to the oven and bake for another 8 to 10 minutes. The peppers are done when the filling is hot and the cheese on top is melted and bubbly.