Preheat the grill to medium heat (about 350°F to 400°F).
In a large skillet, heat 1 tablespoon of olive oil over medium heat.
Add the chopped onion and minced garlic to the skillet and sauté for 3-4 minutes until softened.
Add the ground beef to the skillet and cook until browned, breaking it apart with a spoon, about 6-8 minutes.
Stir in the cooked rice, diced tomatoes, ground cumin, smoked paprika, salt, and black pepper. Cook for an additional 2 minutes to combine flavors.
Remove the skillet from heat and stir in the chopped parsley and half of the shredded cheddar cheese.
Brush the outside of the bell peppers with the remaining 1 tablespoon of olive oil.
Stuff each bell pepper with the beef and rice mixture, pressing down gently to fill completely.
Place the stuffed peppers upright on the grill grates and cover the grill.
Grill the peppers for 20-25 minutes, turning occasionally, until the peppers are tender and slightly charred.
In the last 5 minutes of grilling, sprinkle the remaining shredded cheddar cheese on top of each stuffed pepper and close the grill lid to melt the cheese.
Remove the stuffed peppers from the grill and let them rest for 5 minutes before serving.