Spray the inside of a slow cooker with nonstick spray. Add all of the ingredients except the bay leaves, salt, and pepper. Stir everything gently until evenly combined.
2 lbs beef stew meat, 1 28 oz can fire roasted crushed tomatoes, 2-3 carrots, 4 stalks celery, 1 large yellow onion, 8 oz sliced mushrooms, 1 1/4 cup pearl barley, 2 tbsp minced garlic, 1 tbsp worcestershire sauce, pinch steak seasoning, 1/2 tsp dried thyme leaves, 8-10 cups beef broth