In a large skillet, heat the olive oil over medium heat. Once hot, add the sliced onion and bell pepper. Sauté for about 5-7 minutes until they are softened and beginning to caramelize.
Add the thinly sliced ribeye steak to the skillet. Season with garlic powder, salt, and pepper. Cook, stirring frequently, for about 5-6 minutes until the steak is browned and cooked to your liking.
Remove the skillet from heat and stir in half of the provolone cheese, allowing it to melty slightly with the residual heat.
Slice the slider buns in half and place the bottom halves in a baking dish. If using mayonnaise, spread it evenly on the bottom halves.
Spoon the steak, onion, and pepper mixture generously onto the bottom halves of the slider buns.
Top the filling with the remaining slices of provolone cheese. Place the top halves of the buns over the cheese.
Cover the baking dish with aluminum foil and bake for 10 minutes. Then, remove the foil and bake for an additional 5-10 minutes or until the cheese is bubbly and the tops are golden brown.
Remove from the oven and let cool slightly before slicing into individual sliders.
Garnish with chopped fresh parsley for added color and flavor, if desired.