During his early Soviet period, Ohloblyn authored several monographs on Ukrainian economic history (reprinted in the west in 1971 as "A History of Ukrainian Industry") and began publishing on the Mazepa era of the early eighteenth century. After the war, he continued his studies of seventeenth and eighteenth century Ukraine, publishing books on the Treaty of Pereiaslav of 1654 between the Ukrainian Cossacks and the Muscovite Tsar (1954), the political elite of Left-bank Ukraine in the eighteenth century (1959), and Hetman Mazepa and his era (1960). He also published an important update to Dmytro Doroshenko's pioneering "Ukrainian Historiography" (1957).