Initially, Jef Ongenae worked as an apprentice at an advertising agency. The seeds of his artistry lie in the Second World War, when he became acquainted with the work of Braque, Picasso and Kandinsky through books at his hiding place. Ongenae initially paints figuratively and in the line of Flemish expressionism. From 1946 he opted for geometric abstraction. When he discovered the work of Piet Mondrian during a job at the Stedelijk Museum in Amsterdam in 1950, he decided to further develop his neoplasticism. Ongenae was one of the founders of Liga Nieuw Beelden.