Heat the olive oil in a skillet over medium heat. Add the beef stew meat and brown on all sides for about 5 minutes. Transfer the beef to the slow cooker.
Add the sliced mushrooms, chopped onion, minced garlic, sliced carrots, pearl barley, tomato paste, dried thyme, Worcestershire sauce, salt, and pepper to the slow cooker.
Pour in the beef broth and stir everything to combine.
Cover and cook on low for 7 to 8 hours until the beef is tender and the barley is soft.
Stir in the frozen peas during the last 30 minutes of cooking. Let them heat through before serving.
Notes
Add a splash more broth if the stew thickens too much from the barley during cooking. Leftovers keep well in the fridge for three days and reheat gently on the stove with a little extra broth to loosen the texture.Course: Soup
Cuisine: American
Equipment: Slow Cooker, Skillet