This is a magical little soup. Why, you ask? Because this soup turns into a stew overnight in the refrigerator. The barley in this soup is so absorbent that it will soak up enough liquid to make this beef soup as thick as stew the next day, which works out to be two meals in one!
Allow the meat to sit out at room temperature for approximately 15 minutes. Season all over with salt and freshly ground black pepper.
Heat the vegetable oil in an 8-quart stockpot over high heat. When almost shimmering, add the meat and cook until browned on all sides, about 10 minutes total. Remove the meat to a bowl and reduce heat to medium.
Add the olive oil, onion, carrots, celery, garlic, and thyme. Cook until softened, about 7 to 8 minutes. Stir with a wooden spoon and scrape up the brown bits at the bottom. Add the beef back to the pot and cover with the water. Increase heat to high and bring to a simmer, about 10 minutes.
Once it reaches a simmer, reduce heat to medium-low and cook for 1 ½ hours. Add the barley and cook until done, about 25 to 30 more minutes. Remove from heat and serve.