He has been Visiting Scholar and Humboldt Fellow, Institute fuer Osteuropaische Geschichte, University of Tubingen; International Volkswagen Fellow, Bundesinstitut fur internationale und ostwissenschaftliche Studien, Cologne; Visiting Fellow, Population, East-West Center, Honolulu; Visiting Professor, Economic History, Moscow State University; Advisor to Ministry of Economics of Ukraine; Visiting Professor of Economics, Europe-University Viadrina, Frankfurt/Oder; Assistant Professor of Economics, University of Oklahoma; and Visiting Fellow, Deutsches Institut fuer Wirtschaftsforschung, Berlin.

The author of scores of scholarly articles, Professor Gregory's many books include Women of the Gulag: Portraits of Five Remarkable Lives; Politics, Murder, and Love in Stalin's Kremlin: The Story of Nikolai Bukharin and Anna Larina; Terror by Quota; The Political Economy of Stalinism; The Lost Transcripts of the Politburo; Lenin’s Brain and Other Tales from the Secret Soviet Archives; Socialist and Non-Socialist Industrialization Patterns; Behind the Façade of Stalin's Command Economy; The Global Economy and Its Economic Systems; The Economics of Forced Labor: The Soviet Gulag; Soviet and Post Soviet Economic Structure and Performance (with Robert Stuart); Comparative Economic Systems (with Robert Stuart); Russian National Income, 1885-1913; Essentials of Economics; Principles of Economics (with Roy Ruffin); Restructuring The Soviet Economic Bureaucracy; Before Command: The Russian Economy From Emancipation to Stalin; and The Russian Economy (with Robert Stuart).

Professor Gregory also served on the editorial board of the seven-volume Gulag documentary series, The History of the Stalin Gulag, published jointly by the Hoover Institution and the Russian Archival Service, and he has served on the editorial boards of Comparative Economic Studies, Slavic Review, Journal of Comparative Economics, Problems of Post-Communism, and Explorations in Economic History.