Cut the tops off the peppers and remove the seeds. Discard the tops and the seeds. Set the peppers aside.

In a large bowl combine the rice, ground beef, garlic cloves, 2 c. marinara sauce, pepper, oregano, salt, and Parmesan cheese. Mix well.

Spoon the filling into the 6 peppers.

Place a trivet inside the Instant Pot. Place the peppers on top of the trivet. Pour 2 cups of marinara sauce over top of the peppers.

Place the lid on the Instant Pot and switch to manual. Set on high pressure for 15 minutes.

Allow pressure to release for 5 minutes then release the remaining pressure.

Open the lid and top the peppers with mozzarella cheese. Cover with the lid for 2 minutes to melt the cheese.

Serve hot.