Cooking these incredible stuffed peppers is straightforward if you follow these steps:

1. Preheat the Oven: Set your oven to 375°F (190°C) to get it preheated while you prepare the peppers.

1. Prepare the Peppers: Cut the tops off the bell peppers and remove the seeds. Place them upright in a baking dish.

1. Cook the Meat and Vegetables: In a large skillet over medium heat, add the chopped onion and minced garlic. Sauté until soft, around 3-4 minutes. Then, add the ground meat, cooking until browned.

1. Mix Ingredients: Stir in the cooked rice or quinoa, diced tomatoes, oregano, chili powder, salt, and pepper. Mix well and let simmer for about 5 minutes, allowing the flavors to combine.

1. Stuff the Peppers: Remove the skillet from the heat. Spoon the filling into each pepper, packing it tightly.

1. Add Cheese: Sprinkle shredded cheese on top of each stuffed pepper.

1. Cover and Bake: Tent the baking dish with aluminum foil to keep the moisture in. Bake in the preheated oven for 30 minutes.

1. Uncover and Finish Baking: After 30 minutes, remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and slightly golden.

1. Rest: Once cooked, let the stuffed peppers sit for 10-15 minutes before serving. This allows the flavors to meld and makes them easier to handle.

1. Garnish and Serve: Optionally, sprinkle fresh parsley or cilantro on top for added freshness and color.