Heat 1 tablespoon of vegetable oil in a large skillet over medium-high heat.
Add the sliced onions and sauté for 5-7 minutes until they are soft and caramelized. 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, seasoning with salt and black pepper to taste.
Cook the steak for 2-3 minutes without stirring to get a good sear, then stir and cook for an additional 2 minutes until cooked through.
Return the sautéed onions to the skillet with the steak and mix well.
Divide the steak and onion mixture evenly among the 4 hoagie rolls.
Top each portion with 2 slices of provolone cheese.
Place the sandwiches on a baking sheet and broil in the oven for 1-2 minutes until the cheese is melted and bubbly.
Remove from the oven and serve immediately.