[1] His most significant contribution was to the study of post-Conquest pottery; he was largely responsible for establishing the first chronological framework by which different types of English ceramics could be dated.

However, John Hurst argued that "we should regard Gerald Dunning as the main founding father of medieval archaeology as we know it today in the last quarter of the 20th Century".

[13][14] At the beginning of Dunning's career there was a general ignorance regarding the chronology of later English medieval pottery, and this problem began to occupy his mind during the rescue excavations he undertook in the City of London during the early 1930s.

[15]In 1931 Dunning was awarded the Esher Research Studentship to study specifically medieval pottery and published his first two reports on groups of these objects in 1935.

He was able to discern regional variations in use and production, and through research in France, the Low Countries, Scandinavia and Germany, insular from imported pottery in England, as well as English exports to the Continent.

[18] He collaborated with Sonia Chadwick Hawkes on a study of some of the ornamental migration period grave goods excavated from Anglo-Saxon cemeteries in Kent.

[20] His many other research interests included: French and English schist hones, stone mortars from Purbeck and Caen, the medieval Devon slate trade, black marble Tournai fonts in England and on the Continent, ceramic roof furniture such as chimney pots, finials and roof-tile crests, Iron-Age Swan's neck and Ring-headed pins and late Anglo-Saxon belt buckles.

[21][22] He carried out excavations at a stone circle and cairn in Brecknockshire, Salmonsbury Camp Hillfort, Gloucestershire, an Anglo-Saxon site at Bourton on the Water and at Roman Gloucester, among others.