Pat sirloin steak cubes completely dry with paper towels. Season generously on all sides with salt, pepper, smoked paprika, and garlic powder.
Heat olive oil in a large skillet over medium-high heat. Working in batches, sear steak cubes for 2 minutes per side until golden-brown crust forms. Transfer to crockpot.
In the same skillet, cook diced onion for 3-4 minutes until softened. Add minced garlic and cook 1 minute until fragrant. Pour over steak in crockpot.
Add quartered baby potatoes on top of steak and onions. Do not stir.
In a small bowl, mix beef broth and Worcestershire sauce. Pour evenly over ingredients in crockpot.
Cover and cook on LOW for 6-7 hours or HIGH for 3-4 hours, until steak is fork-tender and potatoes are cooked through.
About 20 minutes before serving, sprinkle shredded cheddar cheese and crumbled bacon (if using) over the top. Cover and let cheese melt.
Serve hot, garnished with fresh green onions and parsley if desired.
