Heat a large skillet over medium-high heat and add olive oil. Add thinly sliced beef sirloin in a single layer, cooking for 3–4 minutes until browned. Remove beef and set aside.

In the same skillet, add the green bell pepper, onion, and mushrooms. Sauté for 5–7 minutes until tender. Add minced garlic in the last minute, then remove from heat.

In a separate skillet, melt butter over medium heat. Add riced cauliflower, seasoning it with salt and pepper. Cook for 5–7 minutes, stirring occasionally.

Return cooked beef to the skillet with vegetables. Drizzle Worcestershire sauce and stir to combine, cooking for an additional minute.

Sprinkle provolone cheese over the mixture. Cover the skillet and cook for 2–3 minutes until the cheese melts.

Assemble the bowls by spooning the beef and vegetable mixture over riced cauliflower. Garnish with freshly chopped parsley and serve immediately.