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 chopped onion and minced garlic; sauté until fragrant and translucent, about 3-4 minutes.
Add the ground beef (or turkey) to the skillet and cook, breaking it apart with a spoon, until browned and cooked through, about 5-7 minutes. Drain excess fat if needed.
Stir in the cooked rice, diced tomatoes, Italian seasoning, salt, and pepper. Mix well and cook for an additional 2-3 minutes to warm through.
Take the skillet off the heat and stir in half of the shredded cheese.
Stuff each bell pepper with the meat and rice mixture, packing it in tightly.
Place the stuffed peppers upright in a baking dish. If there is leftover filling, you can place it around the peppers.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil, sprinkle the remaining cheese on top of each pepper, and bake for an additional 10 minutes or until the peppers are tender and the cheese is melted and bubbly.
Remove from the oven and let cool for a few minutes. Garnish with fresh parsley if desired.
Serve hot and enjoy your delicious stuffed bell peppers!