Prepare your steak by thinly slicing it against the grain; for easier slicing, partially freeze the steak for 30 minutes before cutting.

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

Heat olive oil in a large skillet or on a griddle over medium-high heat. Add the sliced onions and bell peppers to the hot skillet, cooking until softened and lightly caramelized, which should take about 5-7 minutes. Once cooked, remove them from the skillet and set aside.

Add the thinly sliced steak to the same skillet, cooking for 2-4 minutes per side until it is no longer pink. Break up the steak as it cooks with a spatula, then season with salt and pepper to your preference.

Return the cooked onions and bell peppers to the skillet with the steak, mixing them well to combine all ingredients.

Divide the steak and vegetable mixture into four equal portions directly in the skillet, then top each portion with 1-2 slices of provolone cheese.

Cover the skillet with a lid or foil for 1-2 minutes, allowing the cheese to melt and become gooey.

Carefully slice each hoagie roll lengthwise (without cutting all the way through), then place a roll over each portion of the cheesy steak mixture.

Using a spatula, scoop the steak, cheese, and vegetables into each hoagie roll, flipping quickly to keep everything together. Serve immediately and enjoy your homemade Philly Cheesesteak!