Thinly slice the ribeye steak against the grain, which can be easier if the steak is partially frozen.

Slice the onion and bell pepper (if using) into thin strips.

Heat vegetable oil in a large skillet or griddle over medium-high heat.

Add the sliced onions and bell peppers to the skillet and sauté until softened and lightly caramelized, which typically takes about 5-7 minutes.

Push the vegetables to one side of the skillet, then add the thinly sliced steak to the other side and season it with salt and black pepper.

Sear the steak for 2-3 minutes until browned, then use two spatulas to chop and mix the steak with the cooked vegetables.

Continue cooking for another 2-3 minutes, until the steak is fully cooked through and the vegetables are well-integrated.

Divide the steak and vegetable mixture into portions corresponding to the number of hoagie rolls you are using.

Place the slices of provolone cheese over each portion of the mixture on the skillet, or spoon Cheez Whiz generously over the steak, then cover the skillet briefly to allow the cheese to melt (about 1 minute).

While the cheese is melting, lightly toast the hoagie rolls, either on the unused side of the skillet or in a toaster oven, until they are warm and slightly crispy.

Carefully scoop the cheesy steak and vegetable mixture into the toasted hoagie rolls.

Serve your Philly Cheesesteak immediately and enjoy the authentic flavors.