Heat the olive oil in a Dutch oven over medium heat. Add the beef cubes and brown them on all sides. Remove the beef and set it aside.
Add the onion, carrots, and parsnips to the pot. Cook for 5 minutes until the onion softens. Stir in the garlic and cook for 1 minute more.
Sprinkle the flour over the vegetables and stir for 1 minute to coat everything. Return the beef to the pot.
Pour in the ale and beef broth. Add the pearl barley, thyme, bay leaf, salt, and pepper. Stir well to combine.
Bring the mixture to a boil, then reduce to a low simmer. Cover the Dutch oven and cook for 1 hour and 30 minutes, stirring occasionally, until the beef is tender and the barley is cooked through.
Remove the bay leaf before serving.