Bulgur comes from steamed, dried and crushed wheat kernels ground into coarse, medium and fine textures. Barley, on the other hand, comes in a variety of forms, from highly processed pearl barley that has the bran removed and is steamed and polished to hulled barley that has had only the outer husk removed. Replace barley for bulgur in a 1 to 1 ratio and choose the type of barley depending on what you plan to cook.
Bulgur, in any of its grinds, is the key ingredient in tabbouleh, a Middle Eastern salad made with plenty of parsley and combinations of chopped tomatoes, onions, mint, olive oil and lemon juice. With its light texture, pearl barley substitutes most closely for bulgur in tabbouleh. Cracked or ground barleys, known as Scotch barley or barley grits, also pair well with tabbouleh ingredients and give the salad a more chewy texture.
Bulgur's Middle Eastern roots appear in Tunisian fava bean soup and its popularity in Italy shows in the classic Sicilian greens soup made with beets or turnip greens. Pearl barley, too, is frequently used in soups, most frequently in mushroom, beef and barley soup. As with tabbouleh salad, you can substitute more chewy forms of barley in a hearty soup as long as you don't mind a more chewy texture to each bite.
Pilafs, risottos, vegetarian burgers and beef pies and meatballs are all possibilities with either bulgur or barley. You sacrifice authenticity when making a dish such as kibbeh, a Middle Eastern ground beef pie, when using pearl barley instead of bulgur, but the texture and taste won't change too much. Hulled and Scotch barley aren't as successful in main course dishes because their more chewy textures can be overpowering for some people.
Bulgur and barley have very different cooking times. Bulgur cooks in just 10 to 20 minutes depending on the grind and yields about 3 3/4 cups of cooked grain for each cup of uncooked. Pearl barley cooks in about 20 minutes and give you 3 cups of cooked barley for 1 cup of uncooked. And less processed barley, depending on the type, cooks in 45 to 60 minutes and gives 3 1/2 to 4 cups of cooked grains for 1 cup of uncooked.