In a large skillet, melt 2 tablespoons of butter over medium-high heat. Add the sliced steak, salt, and pepper. Cook, stirring occasionally, until browned and cooked through. Remove steak from skillet and set aside.
Add the remaining 2 tablespoons of butter to the skillet. Add the sliced onions and bell pepper. Cook, stirring occasionally, until softened and lightly browned, about 5-7 minutes. Add the minced garlic and cook for 1 minute more until fragrant.
Return the cooked steak to the skillet with the vegetables. Stir to combine and heat through.
While the steak and vegetables are heating, slice the slider buns in half horizontally. Spread mayonnaise on the cut sides of the bottom buns.
Arrange the provolone cheese slices over the steak and vegetable mixture in the skillet. Cover the skillet for about 1-2 minutes, or until the cheese is melted.
Spoon the cheesesteak mixture evenly onto the bottom halves of the slider buns.
Place the top halves of the slider buns over the filling. Serve immediately.
Notes
These sliders are best served fresh. You can also add your favorite hot sauce or a drizzle of steak sauce for extra flavor.