1927 to study in The Hague, MacGonigal was influenced by the work of Anton Mauve and Vincent van Gogh. Touring the coasts of north County Down and County Antrim with Hobson, MacGonigal produced a watercolour series between 1927 and 1930, culminating in his first solo show in 1929 in the St Stephen's Green gallery. He illustrated Kenneth Sarr's 1927 The white bolle-trie: a wonder story. From 1927, MacGonigal was a visiting art teacher at the Royal Hibernian Academy (RHA), and from 1934 was a substitute teacher for the Metropolitan School of Art. From 1924 to 1979, he exhibited with the RHA every year, with an average of 5 works annually. In 1931, he was elected an associate of the RHA, and a full member in 1933. MacGonigal produced rural landscapes, but also cityscapes, genre scenes based in both urban and rural settings, and historically or politically important subjects. Some of his paintings were included in Saorstát Éireann: Irish Free State official handbook (1932). His work was part of the painting event in the art competition at the 1948 Summer Olympics. He was a member of the Academy of Christian Art from 1933. He served as the keeper of the RHA school twice, between 1934 and 1939 and 1950 to 1961, living at the keeper's residence on Ely Place during his second tenure. In 1926, MacGonigal founded the Radical Club, exhibiting work there. His work, A Dublin studio, includes fellow members such as Séan Keating, Harry Kernoff, Frank O'Connor, and Seán O'Sullivan. He also designed the sets for the first production of The silver tassie by Sean O'Casey in Dublin, in the Abbey Theatre in 1935. From 1937 to 1954, MacGonigal served as assistant professor of painting at the newly reformed National College of Art (NCA) under Keating. He succeeded Keating as professor in 1954, remaining in the post until 1969. From 1947 to 1978, he was professor of painting at the RHA, and president from 1962 to 1978. From the 1960s, MacGonigal's work became more abstract, as demonstrated in Composition (1961) which shows influence from cubism. In 1963, he was made an honorary member of the Royal Academy, London, and in 1964 an honorary member of Royal Scottish Academy. MacGonigal resigned as professor in NCA in response to the 1969 student revolt against the conservative curriculum, citing an erosion of the educational authority of the teachers. He was a critic