Heat a large skillet over medium heat. Add oil and butter, then add the sliced onions and bell peppers. Cook slowly, stirring occasionally, until they become soft and slightly caramelized. This should take about 8–10 minutes.

Push the vegetables to one side of the pan and add the thinly sliced beef. Season with salt, pepper, and garlic powder. Let it cook undisturbed for a minute, then start breaking it apart and mixing it with the vegetables. Cook until the beef is browned and juicy.

Using a sharp knife, slice the entire batch of slider rolls in half horizontally without separating them. Place the bottom half into your baking dish.

Evenly spread the hot beef and vegetable mixture over the bottom layer of rolls. Make sure every section gets a good amount of filling. Then layer the provolone cheese generously over the top so it melts beautifully into the meat.

Place the top half of the rolls over the filling, aligning them neatly.

In a small bowl, mix melted butter with parsley and garlic powder. Brush this mixture evenly over the tops of the rolls. This step adds flavor and helps create that beautiful golden finish.

Cover the dish with foil and bake in a preheated oven at 180°C (350°F) for 15 minutes. Then remove the foil and bake for another 5 minutes until the tops are golden and slightly crisp.

Remove from the oven, let them rest for a couple of minutes, then slice and serve. Enjoy them warm while the cheese is perfectly melted.