Slice the beef thinly. For easier slicing, chill the beef in the freezer for 20–30 minutes first.
Cut thin strips against the grain so they stay tender after cooking.
Layer the veggies in the crockpot. Add sliced onions and bell peppers first. This creates a bed that keeps the meat moist and infuses everything with flavor.
Season the beef. Place the sliced beef on top of the vegetables. Sprinkle with salt, pepper, Italian seasoning, and smoked paprika.
Add the minced garlic.
Pour in the liquids. Stir together beef broth, Worcestershire, and soy sauce or tamari. Pour evenly over the beef and veggies.
Cook low and slow. Cover and cook on Low for 6–7 hours or on High for 3–4 hours, until the beef is very tender and the peppers and onions are soft but not mushy.
Taste and adjust. Stir the mixture and taste the broth. Add a pinch more salt or pepper if needed.
If you want a slightly thicker sauce, remove the lid for the last 20–30 minutes to let some liquid evaporate.
Add the cheese. Lay provolone slices over the top, then sprinkle mozzarella if using. Cover and cook for 5–10 minutes, just until the cheese melts and turns gooey.
Assemble the bowls. Spoon a base of warm rice, cauliflower rice, or roasted potatoes into bowls. Top generously with the cheesesteak mixture and some of the savory juices.
Garnish with chopped parsley.
Serve hot. Add hot sauce, red pepper flakes, or a drizzle of spicy mayo if you like extra heat.