1. Preheat oven to 425°F. Press peppercorns evenly onto all surfaces of beef roast. Combine mushrooms, leek and 1-tablespoon oil; toss to coat. Arrange vegetables in single layer on rimmed baking sheet.
2. Place roast on rack in shallow roasting pan. Insert ovenproof meat thermometer so tip is centered in thickest part of beef, not resting in fat. Do not add water or cover. Roast beef in 425°F oven 35 to 40 minutes for medium rare; 45 to 50 minutes for medium doneness. Roast vegetables 35 to 40 minutes or until tender and lightly browned, stirring once.
3. Meanwhile, heat remaining 1-tablespoon oil in 3-quart saucepan until hot. Add barley and cook 3 to 5 minutes or until golden brown, stirring frequently. Add broth and cherries; bring to boil. Reduce heat and simmer; covered, 10 to 12 minutes or until barley is tender. Keep warm.
4. Remove roast when meat thermometer registers 135°F for medium rare; 150°F for medium. Transfer roast to carving board; tent loosely with aluminum foil. Let stand 15 to 20 minutes. (Temperature will continue to rise about 10°F to reach 145°F for medium rare; 160°F for medium.)
5. Stir mushrooms and leeks into barley mixture. Carve roast into slices. Season barley and beef with salt, as desired. Serve with barley.