Preheat your oven to 375°F (190°C). Arrange the bell peppers upright in a baking dish or rimmed baking tray.
Heat olive oil in a large skillet over medium heat.
Add the diced onion and cook until softened, about 4–5 minutes.
Stir in the minced garlic and cook for another minute until fragrant.
Add the ground beef and cook until browned, breaking it apart with a wooden spoon as it cooks.
Stir in the cooked brown rice, diced tomatoes, tomato paste, oregano, and paprika.
Simmer the mixture for 4–5 minutes until slightly thickened.
Season with kosher salt and black pepper to taste.
Fill each pepper generously with the beef and rice mixture.
Bake the peppers for 10–12 minutes until they begin to soften.
Remove from the oven and sprinkle shredded cheddar jack cheese evenly over the tops.
Return to the oven and bake for an additional 5–7 minutes until the cheese is melted and bubbly.
Garnish with fresh parsley and serve warm.
These Easy Stuffed Bell Peppers are best enjoyed fresh from the oven while the cheese is still perfectly melted.