Beef barley soup with wild mushrooms and parsnips

3 tablespoons olive oil
1 1/2 pounds assorted fresh wild mushrooms (such as crimini and oyster), sliced
3/4 pound onions, chopped
2 celery stalks, chopped
4 large garlic cloves, chopped
3 1/2 pounds center-cut beef shank slices (about 3/4 to 1 inch thick)
8 cups canned beef broth
7 cups water
1 1/4 pounds red bell peppers, chopped
1 pound parsnips, peeled, cut into 1/2-inch pieces
1/2 pound carrots, peeled, cut into 1/2-inch pieces
1 3/4 cups pearl barley (about 9 ounces)
1 1/2 cups canned crushed tomatoes with added puree
2 3/4-ounce packages dried porcini mushrooms (see note below), brushed clean of any grit, coarsely chopped
2 tablespoons dried marjoram
1 tablespoon dried thyme

1. Heat oil in heavy large pot over medium-high heat. Add mushrooms and onions. Saute until mushrooms brown, about 18 minutes. Add celery and garlic and stir 1 minute. Add beef shank slices and all remaining ingredients. Bring to boil. Reduce heat to medium-low. Cover and simmer until meat is tender, about 1 1/2 hours. Remove from heat.
2. Using tongs, remove meat from pot. Cool slightly. Remove meat from bones; discard bones and any tough connective tissue. Cut meat into bite-size pieces and return to soup. Season soup to taste with salt and pepper. (Can be made 2 days ahead. Cool slightly at room temperature. Chill uncovered until cold, then cover and keep chilled. Rewarm over medium heat.)