Quirk became so deeply interested in explosives that he started an external degree in chemistry, but his English undergraduate studies were completed from 1945 to 1947 (with the department back in Bloomsbury) and was then invited to take up a research fellowship in Cambridge; however he took up a counter-offer of a junior lectureship at UCL, which he held until 1952. In this period he completed his MA on phonology and his PhD thesis on syntax, and in 1951 became a post-doctoral Commonwealth Fund fellow at Yale University and Michigan State University. Shortly after his return from the US in 1952, he moved to the University of Durham, becoming reader there in 1954, and professor in 1958. He returned to UCL as professor in 1960 and in 1968 succeeded Smith as Quain Professor, a post he held until 1981.