Combine porcinis and 1 cup boiling water in a bowl; cover and let stand 20 minutes or until tender. Drain porcinis in a colander over a bowl, reserving liquid. Line a strainer with a paper towel, and pour porcini liquid through strainer; reserve liquid. Rinse porcinis thoroughly; finely chop.
Heat oil in a large saucepan over medium heat. Add onion and fennel; cover and cook 5 minutes or until softened. Add creminis, garlic, oregano, salt, and pepper; cook 3 minutes or until creminis release moisture.
Stir broth, tomato, sherry, barley, chopped porcinis, and reserved porcini liquid into cremini mixture; bring to a boil. Reduce heat; simmer 10 to 12 minutes or until barley is tender. Divide soup evenly among 4 bowls.