Use a sharp knife to trim the tops off of 4 bell peppers . Remove the stems and dice the pepper tops to add to the filling. Trim the bottom off of the peppers which will stabilize them in the pan.
Hollow out the bell peppers by laying the pepper on its side on a cutting board. Use a sharp knife and run it around the inside of the flesh to remove the core.
Heat 1 tablespoon olive oil in a skillet over medium-high heat. Once the skillet is hot, add 3/4 pound ground beef and cook until it's almost cooked through. Add 1/2 cup diced onion and diced peppers from the tops of the peppers. Cook for a few minutes until the vegetables begin to turn soft.
Add the 1 cup rice (cooked) and 1/2 cup of tomatoes, stir and simmer for a few minutes longer. Once combined, transfer the ground beef mixture to a bowl.
Wipe out the skillet and add a tablespoon of olive oil to the skillet and heat it over medium heat, once the oil is hot, add the garlic and cook for few minutes. Add the tomato sauce and oregano; reduce the heat to low heat.
Use a spoon to fill the bell peppers with the ground beef and rice mixture. Place each stuffed pepper into the skillet with the tomato sauce and spoon a little bit of the sauce over the top of each pepper. Cover the pan and cook on low heat for 30 minutes.
Notes
Substitutes:Ground beef can be replaced with an equal amount of ground chicken, turkey or pork.Tomato sauce can be replaced with tomato puree or diced tomatoes.Add a teaspoon of Worcestershire or salt and pepper to taste.