In the summer of 1820 he accepted an appointment to the professorship of the Theory and Practice of Medicine, and of Materia Medica and Therapeutics in Dartmouth College, where he delivered his first course of lectures in the following autumn. He was also made Professor of Botany, and his lectures upon Physiology were among his most valuable contributions to medical literature. He took up his permanent residence in Hanover, in August, 1821, and from this time to the close of his connection with the college he was most faithful to all its interests. In 1825 he was appointed to the chair of Intellectual Philosophy in the Academical department of the college, a position which he filled with the ability that distinguished him elsewhere. The address delivered by him on the occasion of his induction into this professorship, upon the "Comparative Importance of the Study of Mental Science," was thus far, perhaps, his most successful literary effort. Clear, comprehensive, and abounding in passages of remarkable beauty and force, it established the reputation of its author both as a writer and a metaphysician. In 1835 was published his "First Lines in Physiology," a treatise which received the highest commendation both at home and abroad. It passed through three editions, and although the rapid advance in physiological science since its publication has long since led to its disuse, it will still be admired by medical scholars for the purity of its style and the learning it everywhere displays. In the spring of 1837, Dr. Oliver closed his connection with the college, and returned to Cambridge, where he was temporarily residing at the time of his appointment, again to resume the practice of his profession. He, however, delivered a course of lectures at the Dartmouth Medical School in the autumn of this and the following year. He was also induced, in 1840, after declining professorships both in St. Mary's College, Baltimore, and in Pennsylvania University, to deliver a course of lectures on Materia Medica at the Medical College of Ohio, but he resigned the chair at the close of the session, and returned again to Cambridge, where he resided to the close of his life. Although in declining health at this time, he did not relinquish professional practice until within a few months of his death, which took place on the 1st of June, 1842.