Preheat and prep. Heat your oven to 375°F (190°C).
Lightly oil a baking dish large enough to fit the peppers upright.
Prepare the peppers. Slice off the tops, remove seeds and membranes, and trim the bottoms slightly if needed so they stand. Place them in the baking dish, open side up.
Par-bake for tenderness. Brush the insides with a little olive oil and sprinkle with salt. Bake uncovered for 10 minutes to soften slightly.
This helps them cook evenly later.
Cook the filling base. Warm 1 tablespoon olive oil in a large skillet over medium heat. Add onion and cook until translucent, about 4 minutes. Stir in garlic and cook 30 seconds until fragrant.
Brown the protein. Add ground turkey (or your choice) and cook, breaking it up, until no longer pink, 5–7 minutes.
Season lightly with salt and pepper as it cooks. For a vegetarian version, sauté mushrooms until browned, then add black beans and heat through.
Season and sauce. Stir in cumin, smoked paprika, oregano, and red pepper flakes if using. Add tomato paste and cook 1 minute to caramelize.
Pour in crushed tomatoes or sauce and simmer 3–4 minutes until slightly thickened.
Fold in grains and add-ins. Stir in cooked rice or quinoa and any optional veggies like corn or zucchini. Taste and adjust salt and pepper. The mixture should be savory and well-seasoned.
Stuff the peppers. Spoon the filling into each pepper, packing gently and mounding slightly on top.
Sprinkle with cheese if using.
Bake to finish. Cover the dish loosely with foil and bake 20 minutes. Remove foil and bake another 10–15 minutes, until peppers are tender and cheese is melted and golden.
Garnish and serve. Let rest 5 minutes. Top with chopped parsley or cilantro.
Serve warm with a simple green salad or roasted potatoes.