Preheat your oven to 375°F (190°C). Cut the tops off the bell peppers and carefully remove the seeds and membranes. If needed, trim a small slice from the bottoms so they stand upright. Brush the outsides lightly with olive oil and arrange them in a baking dish.
In a large skillet over medium heat, cook the ground beef until no longer pink, about 5-7 minutes. Add the diced onions and continue cooking until soft and translucent. Add the minced garlic and cook for an additional 1 minute until fragrant. Drain any excess grease if necessary.
Add the cooked rice, drained diced tomatoes, tomato paste, oregano, basil, and paprika to the skillet. Season with salt and pepper to taste. Stir well to combine all ingredients and allow the mixture to simmer for about 5 minutes, letting the flavors meld together.
Spoon the filling mixture evenly into the prepared bell peppers. Cover the baking dish with aluminum foil and bake for 30 minutes. Remove the foil, sprinkle the tops with shredded cheese, and return to the oven uncovered for an additional 10-15 minutes until the cheese is bubbly and the peppers are tender.
Remove from the oven and let stand for 5 minutes. Garnish with freshly chopped parsley and serve hot, straight from the baking dish for a true family-style presentation.