He graduated from the Department of Zoology, Tokyo Imperial University in 1941, and in the following year took up an assistant position in the Natural Resources Institute (資源化学研究所) of the Interior Ministry.
Ōyama received his PhD in 1955, and almost immediately left for a period of postdoctoral research with Dr. Myra Keen at Stanford University in California that lasted until April 1957.
In 1979, Ōyama retired from the Geological Survey and founded a research laboratory at Toba Aquarium in Mie, also housing his vast library of paleontological and malacological literature.
Together with Tadashige Habe and Tokubei Kuroda he was commissioned by the publisher Maruzen to co-author The Seashells of Sagami Bay (1971) on behalf of the Imperial Household.
Ōyama built up a massive personal library of books and papers on Paleontology and Malacology that included many major nineteenth-century western works and a substantial body of Russian literature.