Oshinomi graduated with a Bachelor degree in Engineering from Yokohama National Univerity in 1965 before taking taking up an one year Assistant post there.
He worked in the Architectural Design Department of Kajima Corporation from 1966 before founding his own architectural design company, K/O Design studio, in 1993. K/O Design engages in a plethora of designs from skyscrappers, to residences, furniture, door handles and even fashion.
Oshinomi is a Visiting Professor at the Tokyo Institute of Technology University as well as the Yokohama National University Graduate School. He has published two books, "Interior Watching" in 1985 and "Planning and Detailing "Intelligent Buildings"" in 1987.