Returning to the United States once more, he served as an assistant to Burgess for six years, and immediately began teaching the course on "Political History of the Colonies and the American Revolution" in 1891.

"[1] Along with Charles McLean Andrews, George Louis Beer (who was Osgood's student at Columbia), and other Imperial School historians, he took a view of the colonial period that focused on its imperial ties with Great Britain, which he first set forth in an early article ("England and the Colonies") in Political Science Quarterly (Sept. 1887) in which he was critical of the partisanship that had characterized so many studies of that era, where the colonists had been portrayed as heroic and virtuous while the British were the forces of evil.

Osgood then spent years working on the four-volume sequel, The American Colonies in the Eighteenth Century, which he had all but finished at the time of his death—a chapter on slavery was yet to be written, as well as the final editing.

[7] Even while working on these various projects, Osgood continued to teach and supervise doctoral dissertations at Columbia, and among his students were William Robert Shepherd, Charles Austin Beard, and Arthur Meier Schlesinger.

Biographer Gwenda Morgan concludes: Osgood brought a new sophistication to the study of colonial relations posing the question from an institutional perspective, of how the Atlantic was bridged.

He was the first American historian to recognize the complexity of imperial structures, the experimental character of the empire, and the contradictions between theory and practice that gave rise, on both sides of the Atlantic, to inconsistencies and misunderstandings....