Heat 3 tbsp butter in a large cast iron skillet on medium high to high heat.
Once the skillet is hot, add the sliced green pepper, yellow onion, and mushrooms. Sear the vegetables for 7-8 minutes or until slightly charred and tender.
Remove the vegetables to a clean plate.
Add 2 tablespoons of butter to the skillet and return to the heat.
Sear the thinly sliced ribeye for 7-8 minutes, or until cooked through and the skillet is dry.
Remove from the heat and add the vegetables back into the skillet. Toss to mix the vegetables and the meat together.
Place the provolone inside the hoagie rolls and fill with the cheesesteak veggie/meat mixture. Serve immediately.