Preheat your oven to 375°F (190°C).
Cut the tops off the bell peppers and remove the seeds and membranes. Set aside.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and garlic, sautéing until the onion is translucent, about 3-4 minutes.
Add the ground turkey to the skillet, breaking it apart with a spoon. Cook until browned and cooked through, about 5-7 minutes.
Stir in the cooked rice, drained diced tomatoes, Italian seasoning, salt, and black pepper. Cook for an additional 2-3 minutes until everything is heated through.
Remove the skillet from heat and stir in half of the shredded cheese.
Stuff each bell pepper with the turkey and rice mixture, packing it in gently. Place the stuffed peppers upright in a baking dish.
Top each stuffed pepper with the remaining shredded cheese.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, until the cheese is bubbly and golden.
Remove from the oven and let cool for a few minutes. Garnish with fresh parsley if desired before serving.