Prep the steak: Freeze the steak for 20–30 minutes to firm it up, then slice thinly against the grain. Pat dry with paper towels.
Toss with a pinch of salt, pepper, and half the oregano.
Slice the veggies: Cut onions and peppers into thin strips. Slice mushrooms if using. Mince the garlic.
Preheat the pan: Heat a large skillet or cast-iron pan over medium-high until hot.
Add 1 tablespoon oil.
Sauté the veggies: Add onions and peppers with a pinch of salt. Cook 6–8 minutes, stirring occasionally, until softened and lightly browned. Add mushrooms and cook 2–3 minutes more.
Stir in garlic for 30 seconds. Transfer veggies to a bowl.
Sear the steak: Add remaining oil and the butter to the hot pan. Increase heat if needed.
Spread steak in a single layer. Don’t crowd the pan—cook in batches if necessary. Sear 1–2 minutes per side until browned but still tender.
Season and deglaze: Return all steak to the pan.
Add Worcestershire, smoked paprika, remaining oregano, and black pepper. Scrape up brown bits. Taste and adjust salt.
Combine: Add the sautéed veggies back to the pan.
Toss with the steak until everything is hot and well mixed.
Add the cheese: Lay provolone slices over the mixture. Cover the pan for 1–2 minutes to melt. Alternatively, stir in shredded cheese for an even coating.
Optional base: If using cauliflower rice, quickly sauté it in a separate pan with a bit of oil and salt until tender (5–6 minutes).
Spoon into bowls.
Serve: Spoon the cheesy steak-and-veg mixture into bowls. Garnish with chopped parsley. Add extra cracked pepper if you like.