Heat 1 tablespoon of vegetable oil in a large skillet over medium-high heat.
Add the sliced onions and cook, stirring occasionally, until they are soft and caramelized, about 7 minutes. Remove onions from the skillet and set aside.
Add the remaining 1 tablespoon of vegetable oil to the skillet and increase heat to high.
Add the thinly sliced ribeye steak to the skillet in a single layer. Season with salt and black pepper.
Cook the steak without stirring for about 2 minutes to brown, then stir and cook for another 2-3 minutes until fully cooked.
Return the caramelized onions to the skillet with the steak and mix well.
Divide the steak and onion mixture evenly among the four hoagie rolls.
Top each with 2 slices of provolone cheese.
Place the sandwiches on a baking sheet and broil in the oven for 1-2 minutes or until the cheese is melted and bubbly.
Remove from the oven and serve immediately.