1 Can of corn optional*
Preheat the oven to 400 degrees F = 205 C. Cut the tops off each pepper, reserve them and hollow out the insides of the peppers of any seeds and seed walls. Sprinkle the insides with a pinch salt and a pinch pepper and set aside.
Heat 1 teaspoon of the oil in a large nonstick skillet over medium heat and add the garlic and onions. Cook until softened, 3 minutes, and then add the beef. Add 1/2 teaspoon salt and 1/4 teaspoon pepper. Cook, breaking up the meat with a wooden spoon, until no longer pink. Stir in 1 tablespoon of the tomato sauce until it coats the meat and is slightly darkened.
Boil the rice in another cooker. Cook until almost soft. Remove the sauce from the heat and add the rice and corn. Set aside until the liquid is absorbed and the mixture is cooled slightly.
Divide the filling among the peppers and place the tops back on. Set the peppers upright in a small baking dish. Use the remaining sauce in the pan. Pour into the dish around the peppers. Bake until the peppers are tender about 1 hour 15 minutes.
Carefully transfer the peppers to a serving dish, decorate with fresh parsley. Use the sauce in the baking dish if preferable.