Preheat your oven to 375°F (190°C) and lightly grease a small baking dish.
Slice the tops off the bell peppers, remove the seeds and membranes, and set the peppers upright in the baking dish.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and minced garlic, sautéing until translucent and fragrant.
Add the ground turkey to the skillet, breaking it up with a spoon, and cook until completely browned and no longer pink.
Stir in the cooked brown rice, tomato puree, dried oregano, sea salt, and black pepper, mixing until well combined and heated through.
Remove from heat and fold in the fresh chopped parsley.
Spoon the turkey and rice mixture into the hollowed bell peppers, pressing down gently to pack the filling.
Sprinkle the grated parmesan cheese evenly over the top of each stuffed pepper.
Pour 2 tablespoons of water into the bottom of the baking dish to help steam the peppers, then cover the dish tightly with foil.
Bake for 25 minutes, then remove the foil and bake for an additional 5-10 minutes until the peppers are tender and the cheese is golden.