Preheat your oven to 350°F (175°C) and line a baking dish with parchment paper.

In a skillet over medium heat, sauté onions and bell peppers in oil until softened (about 5-7 minutes). Add garlic powder during cooking.

Add the thinly sliced steak to the skillet, season with salt and pepper, and cook until just browned (3-4 minutes). Mix well.

Slice the slider buns in half horizontally without separating them. Place the bottom halves in the baking dish.

Spoon the beef mixture onto each bun base and top with provolone cheese slices.

Cover with the top halves of the buns, brush with melted butter, then bake for 15-20 minutes until cheese is melted.