Step 1: Pre-roast the Peppers

Preheat your oven to 400°F (about 200°C). Cut each bell pepper in half lengthwise through the stem, then gently pull out the seeds and any tough white membranes so you have six clean “boats” ready to fill.​

Arrange the pepper halves, cut side up, in a baking pan so they sit snugly and don’t tip over as they roast and later when they’re stuffed. Slide the pan into the preheated oven and bake the peppers for about 20 minutes, just until they are slightly softened and beginning to look a bit wrinkled around the edges; this head start ensures the peppers are tender by the time the filling and cheese are cooked.​​

Step 2: Cook and Crumble the Beef

While the peppers are roasting, heat a large skillet over high heat; if the skillet is not well-seasoned cast iron, add a thin film of oil to prevent sticking. Add about half of the frozen sliced beef to the hot pan, keeping the pieces in a relatively even layer so they sear instead of steam; working in batches is essential because crowding the pan traps moisture and leads to pale, tough meat.​​

As the beef begins to brown, use a sturdy spatula to chop and scrape the meat, breaking it into fine shreds; the goal is a loose, cheesesteak-style texture rather than large strips. Cook until the beef is no longer pink and has released a good amount of fat, then transfer the cooked meat to a plate and repeat with the remaining beef until all of it is browned, finely broken up, and cooked through.​​

Step 3: Drain Fat and Sauté Vegetables

Once all the beef is cooked and removed from the skillet, carefully pour off most of the rendered fat, leaving behind just under 2 tablespoons to cook the vegetables; this small amount of flavorful fat replaces extra oil and carries the beefy taste into the mushrooms and onions. Return the skillet to medium-high heat and add the thinly sliced onions and cremini mushrooms, tossing them in the reserved fat to coat every slice lightly.​​

Sauté, stirring occasionally, until the onions turn soft and lightly golden and the mushrooms have released their moisture and taken on some caramelized color, which should take about 5 to 6 minutes; this step concentrates their flavor so the filling tastes rich instead of watery. When the vegetables are softened and slightly browned, add the cooked beef back into the skillet and fold it through the onions and mushrooms so everything is evenly combined.​​

Step 4: Season and Add Shredded Cheese

With the beef and vegetables together in the skillet, sprinkle a generous pinch of salt, a few grinds of black pepper, and a good shake of granulated garlic over the mixture; granulated garlic is used here instead of fresh because it offers gentle garlic flavor without overpowering the sweet onions and savory beef. Taste a small bite and adjust the seasoning, adding a little more salt or pepper if the mixture tastes flat, remembering that the cheese you add next will also contribute saltiness.​​

Turn off the heat and immediately scatter the shredded cheese over the hot filling, folding it through with a spatula until the cheese melts and binds everything together in a slightly creamy, cohesive mixture that will hold nicely in the pepper halves. The filling should look glossy and cheesy, with no dry pockets of meat or vegetables, and still be loose enough to spoon easily.​​

Step 5: Stuff and Top the Peppers

By this time, the peppers should be mostly tender from their initial roast; remove the baking pan from the oven and let the peppers cool just enough so you can handle the pan comfortably. Using a spoon, carefully divide the cheesesteak mixture among the pepper halves, mounding it up slightly so each pepper is generously filled from end to end.​

Lay a slice of your chosen cheese over the top of each stuffed pepper, allowing it to drape slightly over the sides; this creates that classic, gooey cheesesteak finish and also helps keep the filling moist as it reheats in the oven. If the slices are large, you can trim or fold them so they fit neatly over each pepper while still giving full coverage.​​

Step 6: Final Bake and Serve

Return the pan of stuffed peppers to the 400°F oven and bake for about 10 minutes, or just until the cheese on top is fully melted and beginning to bubble; if you like a bit of golden color, you can switch the oven to broil for the last minute, watching closely so the cheese does not scorch. The filling is already cooked, so this stage is mostly about bringing all the components to the same hot temperature and letting the flavors meld in the pepper “shells.”​​

Once baked, let the peppers rest for a few minutes so the cheese settles slightly and the filling firms up enough to slice and serve without spilling. Serve the cheesesteak stuffed peppers hot, perhaps with a crisp salad or simple roasted vegetables on the side to complete a satisfying meal that feels hearty without relying on bread.