If the ribeye steak is not already thinly sliced, place it in the freezer for about 20-30 minutes to firm it up. Once firm, slice the steak as thinly as possible against the grain.

Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add the sliced onions (and bell pepper if using) to the skillet and cook, stirring occasionally, until they are softened and slightly caramelized, about 5 minutes.

Push the onions to one side of the skillet and add the sliced ribeye steak to the other side. Season with salt and pepper. Cook the steak for about 3-5 minutes, stirring occasionally until it is browned and cooked through.

Combine the steak with the onions in the skillet. Divide the mixture into four equal portions and place two slices of provolone cheese on top of each portion. Cover the skillet with a lid for about 1-2 minutes, until the cheese is melted.

While the cheese is melting, lightly toast the hoagie or sub rolls in another skillet or under the broiler for added texture.

Using tongs, scoop each portion of the steak and cheese mixture into the toasted rolls. Serve hot, optionally wrapping in aluminum foil to keep warm.