Heat olive oil in a large skillet over medium-high heat. Add the sliced steak and cook until browned, breaking it apart with a spoon. Remove steak from skillet and set aside.
Add the sliced onion and bell pepper to the same skillet. Cook until softened, about 5-7 minutes. Season with salt and pepper.
Return the steak to the skillet with the vegetables. Stir to combine.
In a small bowl, mix together mayonnaise, ketchup, and Worcestershire sauce. Spread this mixture evenly over the cut sides of the slider rolls.
Place the bottom halves of the rolls in a greased 9×13 inch baking dish.
Spoon the steak and vegetable mixture evenly over the bottom halves of the rolls.
Top with the provolone cheese halves.
Place the top halves of the rolls over the cheese.
Pour the melted butter evenly over the tops of the rolls. Sprinkle with poppy seeds, if desired.
Cover the baking dish tightly with foil.
Bake for 15-20 minutes, or until the rolls are golden brown and the cheese is melted.
For pull-apart sliders, cut between the rolls before serving.
Notes
For make-ahead, assemble the sliders up to the buttering step, cover tightly, and refrigerate for up to 24 hours. Bake as directed, adding a few extra minutes to the baking time.
To reheat, cover with foil and bake at 300°F (150°C) until heated through.
You can substitute other cheeses like Swiss or cheddar.
For thinner steak slices, partially freeze the steak before slicing.