In a large skillet, heat olive oil over medium-high heat. Brown the beef tips in batches, just until seared. Transfer to the slow cooker.
In the same skillet, add diced onions and garlic. Sauté for 2–3 minutes, then deglaze the pan with beef broth, scraping up all the flavorful bits.
Pour the onion-garlic-broth mixture into the slow cooker. Add Worcestershire sauce, onion powder, garlic powder, thyme, salt, and pepper. Stir well to combine.
Cover and cook on LOW for 7–8 hours or on HIGH for 4–5 hours, until beef is tender.
About 20 minutes before serving, mix cornstarch and water in a small bowl and stir into the slow cooker. Cover and cook on HIGH until the gravy thickens.
Meanwhile, cook the egg noodles according to package instructions. Drain and set aside.
Serve the beef tips and rich gravy over warm noodles. Garnish with fresh parsley.
