Preheat oven to 400°. In a small saucepan, prepare rice according to package instructions. Heat oil in a large skillet over medium heat. Add onion and cook until soft, about 5 minutes. Stir in tomato paste & garlic. Cook until fragrant, about 1 minute. Cut bell peppers in half and remove all seeds and internal membrane.
For Best Results, gently massage Barbacoa packages for 20 seconds prior to heating to separate meat into shreds. Empty contents of product into microwave safe dish and cover with paper towel. Microwave for 45 seconds stirring halfway. Let rest for 1 minute.
Add beef to tomato paste mixture then stir in cooked rice and diced tomatoes. Season with oregano, salt and pepper. Simmer until liquid has reduced, about 5 minutes. Place peppers cut-side-up in a medium baking dish and drizzle with oil. Add beef & tomato mixture to each pepper and top with cheese, then cover baking dish with foil and bake for 35 minutes. Remove the foil and continue baking until cheese is bubbly, 10 minutes.
Garnish with parsley before serving.