Follow these detailed steps carefully to ensure your taco stuffed peppers come out perfectly cooked, incredibly flavorful, and ready to impress.

1. Prepare the Peppers and Oven: First, preheat your oven to 400°F (200°C). This is a crucial step to ensure the peppers cook evenly and become tender. While the oven heats up, prepare your bell peppers. Slice each pepper in half lengthwise, from the stem to the base. Carefully remove the seeds and the white membranes from the inside, creating hollow “boats.” Arrange the pepper halves, cut-side up, in a 9×13 inch baking dish or on a large baking sheet. Drizzle them lightly with a touch of olive oil and a sprinkle of salt and pepper. This pre-seasoning step adds flavor directly to the pepper itself.
2. Pre-Bake the Peppers (Optional but Recommended): For a more tender pepper, it’s highly recommended to give them a head start in the oven. Place the prepared baking dish of peppers into the preheated oven and bake for 15-20 minutes. This process, known as par-baking, softens the peppers so they will be perfectly tender-crisp by the time the filling is cooked through, preventing a crunchy, undercooked result.
3. Start the Taco Filling: While the peppers are in the oven, you can begin making the delicious filling. Place a large skillet or Dutch oven over medium-high heat and add the olive oil. Once the oil is shimmering, add the finely chopped yellow onion and cook, stirring occasionally, until it becomes soft and translucent, which should take about 4-5 minutes. Add the minced garlic and cook for another minute until it is fragrant. Be careful not to burn the garlic.
4. Brown the Beef: Add the lean ground beef to the skillet with the onions and garlic. Use a wooden spoon or spatula to break the meat apart. Cook the beef until it is browned all over and no pink remains, which usually takes about 7-8 minutes. As it cooks, the fat will render out. Once browned, carefully drain off any excess grease from the skillet. This step is key to a flavorful but not greasy filling.
5. Season and Simmer: Return the skillet to the heat. Sprinkle the packet of taco seasoning over the browned beef, and stir well to coat the meat completely. Now, pour in the entire can of undrained diced tomatoes and add the rinsed and drained black beans. Stir everything together until well combined. Bring the mixture to a gentle simmer, then reduce the heat to low. Let it simmer for 5-7 minutes, allowing the flavors to meld together and the sauce to thicken slightly.
6. Finalize the Filling: Turn off the heat. Stir the cooked rice (or quinoa) into the beef mixture. This will absorb some of the excess liquid and add wonderful body to the filling. Next, add 1 cup of the shredded Mexican cheese blend directly into the skillet. Stir until the cheese is melted and fully incorporated. This makes the filling extra rich, creamy, and helps it hold together inside the peppers. Give the filling a final taste and adjust with salt and pepper if needed.
7. Stuff the Peppers: Carefully remove the par-baked peppers from the oven. Using a large spoon, generously fill each pepper half with the beefy taco mixture. Don’t be shy—mound the filling up over the top of each pepper.
8. Bake to Perfection: Top each stuffed pepper with the remaining 1 cup of shredded cheese, dividing it evenly among them. Place the baking dish back into the 400°F (200°C) oven. Bake for another 15-20 minutes, or until the peppers are fully tender, the filling is heated through, and the cheese on top is bubbly, melted, and slightly golden brown.
9. Rest and Serve: Once baked, remove the peppers from the oven and let them rest in the pan for about 5 minutes. This allows the filling to set up slightly, making them easier to serve. Garnish with your favorite toppings and serve immediately.