Prep your base: Cook brown rice, quinoa, or cauliflower rice according to package directions.
Fluff and keep warm.
Slice everything thin: Cut chicken, peppers, onions, and mushrooms into thin strips. Thin slices cook fast and feel cheesesteak-authentic.
Season the chicken: In a bowl, toss chicken with smoked paprika, onion powder, garlic powder, half the salt, and black pepper. Add 1 teaspoon oil to help spices coat evenly.
Sear the chicken: Heat 1 tablespoon oil in a large skillet over medium-high.
Add chicken in a single layer. Cook 4–6 minutes, stirring once or twice, until just cooked through with browned edges. Transfer to a plate.
Cook the veggies: Add another teaspoon of oil if needed.
Add onions and peppers with a pinch of salt. Cook 5–7 minutes until softened but still bright. Stir in mushrooms and cook 2–3 minutes more.
Add garlic and cook 30 seconds until fragrant.
Build flavor: Return chicken to the pan. Stir in Worcestershire, soy or tamari, and vinegar. Toss to coat and let everything bubble for 1–2 minutes so the flavors concentrate.
Melt the cheese: Lower heat to medium.
Lay provolone slices over the chicken and veggies, or sprinkle with shredded cheese. Cover the pan for 1–2 minutes until melted and gooey.
Taste and adjust: Add remaining salt if needed. Finish with parsley and a dash of hot sauce if you like heat.
Assemble the bowls: Divide the warm grain base among bowls.
Top with the cheesy chicken-and-veggie mixture. Spoon any pan juices over the top for maximum flavor.