While overseas, he performed research in the laboratory of the forest scientist Jack Harley in Oxford, looking into the symbiosis between fungi and forest trees, and spent some time performing taxonomic studies at the Royal Botanic Gardens, Kew. In 1952, after his return to Austria, he was offered a post at the Federal Institute for Forestry Research at Imst, which he accepted. There, he applied what he had learnt about the symbiosis of fungi and trees to the practical issue of reforestation in the Alps, and developed a method for the use of ectomycorrhizal fungi for the "inoculation" of trees, which later became standard practice around the world. Moser remained with the Federal Institute until 1968. Moser continued his taxonomic studies while at the Federal Institute. In 1953, he published the first edition of Die Blätter und Bauchpilze (Agaricales und Gastromycetes) [The Gilled and Gasteroid Fungi (Agaricales and Gastromycetes)], a monographic treatment of the Agaricales and Gastromycetes of central Europe. The book listed 3150 taxa. It served as an update to the mycologist Adalbert Ricken's 1918 Vademecum für Pilzfreunde [Handbook for Mushroom Hunters], though reflecting Moser's taxonomic views, which were highly influenced by Singer. The book was part of the series Kleine Kryptogamenflora von Mitteleuropa, edited by the botanist Helmut Gams. The work, which became known simply as "Moser", was updated and republished numerous times over the following decades, and translated into both Italian and English, with the latter being by the naturalist Roger Phillips. Some later versions of the book had a different focus. The mycologist René Pomerleau described a 1967 edition, Röhrlinge und Blätterpilze [Pored and Gilled Mushrooms], containing descriptions of 2547 species, as "probably the most complete and up-to-date descriptive flora of this group of fungi for central Europe". Die Blätter und Bauchpilze (Agaricales und Gastromycetes) became important for the study of biodiversity in and out of Europe, with Singer calling the book a "much used and appreciated field manual". The work continued to be used as a standard reference for several decades; in 1981, it was still, in the words of the mycologist Richard P. Korf, "the most-used and most authoritative handbook on larger European fleshy fungi". University of Innsbruck In 1956, while still a researcher at the institute, Moser began lecturing on microbiology at the University of Innsbruck, with the title of Privatdozent. He continued to publish while teaching. His monograph Die Gattung Phlegmacium (Schleimköpfe)