Preheat oven to 375 degrees F.
In a large skillet, add oil and heat over medium-high heat.
Add onion and bell pepper, and cook until they are well cooked and softened, about 10 minutes.
Add garlic and cook one more minute.
Season with salt and pepper.
Remove veggies from pan.
Add thinly sliced steak to the same pan over medium-high heat and cook until no longer pink.
Add beef broth and Worcestershire, and cook another 8-10 minutes, until the broth has reduced.
Meanwhile, make the butter topping.
Combine melted butter, dijon, garlic powder, minced onion, and salt.
Place bottom of the slider buns in a 9x13” pan.
Distribute beef among the buns, and top with veggies.
Top veggies with cheese and bun tops.
Brush thoroughly with butter topping.
Cover with foil and bake in preheated oven for 12-15 minutes, until cheese is melted through.
Serve and enjoy!