Onat entered Istanbul Technical University in 1926 and was sent on to the technical university in Zurich, where he studied under Otto Rudolf Salvisberg and absorbed a disciplined Swiss modernism. He returned to Turkey in 1934 to teach, became the first dean of Istanbul Technical University's new Faculty of Architecture in 1944, and served as its rector from 1951 to 1953. With Orhan Arda he won the 1942 international competition for Atatürk's mausoleum, and that building occupied him for the rest of his working life. His architecture belongs to what Turkish historians call the Second National Architectural Movement: symmetrical, monumental, faced in cut stone, drawing on Seljuk and Ottoman precedent without copying it. He also built the Istanbul Justice Palace and the presidential secretariat at Çankaya. In October 1960 he was among the 147 academics dismissed from Turkey's universities; he died the following year.
