Place the beef in the freezer for 20 to 30 minutes before preparing. This firms up the meat, allowing you to slice it paper-thin against the grain with ease.
Heat a large flat-top griddle or cast-iron skillet over medium-high heat. Add 1 tablespoon of olive oil, followed by the sliced onions, green bell peppers, and red bell peppers. Sauté for 5 to 7 minutes until softened and nicely caramelized. Remove the vegetables from the pan and set them aside.
Add the remaining 1 tablespoon of olive oil to the hot skillet. Spread the thinly sliced beef in an even layer. Season generously with salt and black pepper. Cook for 3 to 4 minutes, flipping occasionally until browned and fully cooked.
Return the caramelized onions and peppers to the skillet, folding them into the cooked beef. Divide the mixture into 4 equal, rectangular portions directly on the cooking surface.
Place two slices of provolone cheese over each portion of the meat and vegetable mixture. Allow the cheese to melt completely for about 1 to 2 minutes.
Place a split and toasted long bread roll face-down onto each melted cheese and meat portion. Slide a wide spatula firmly underneath the meat and carefully flip the entire sandwich right-side up.
Garnish with chopped fresh parsley and serve immediately while hot.