Beef Mushroom Barley Soup

2 pounds beef stew meat, cut into small pieces

1 tablespoon vegetable oil

1 ½ onion, chopped

3 stalks celery, chopped

3 carrots, chopped

7 ½ cups beef stock

8 ounces pearl barley

1 pound mushrooms, sliced

Cook beef stew meat in a large skillet over medium heat until completely browned, 5 to 7 minutes; transfer to a large soup pot.

Heat vegetable oil in the same skillet over medium heat; cook and stir onion, celery, and carrot in the hot oil until the onions are tender, about 5 minutes. Add the vegetable mixture to the beef in the pot.

Pour beef stock into the pot.

Stir pearl barley into the stock.

Place soup over medium-low heat, bring to a simmer, and cook, stirring occasionally, until the beef is completely tender, about 2 hours.

Stir mushrooms through the soup; cook 1 hour more.