If Gál could thank the war for anything, it was the enforced break from his own early works, giving him the necessary critical distance only to publish those works of which he was later still convinced. This applied to only a fraction of the available compositions from the time before 1918; but he still acknowledged these select works even in old age. The works composed before he was thirty often only give hints as to the face of the later, characteristic Gál in isolated features, but they all have in common a lively freshness and naturalness as well as a well-developed early sense of form and clarity.

With the end of the First World War began the rebuilding of Gál's musical career in Vienna. The next decade could be seen as decisive for his development as a composer as well as for his reception, and his own individual style was largely established during this period. But in view of the post-war political and material crisis in Austria - not to mention the galloping inflation which by 1922 had reduced the currency to one 14,000th of its pre-war value - the circumstances for the young composer were at first extremely difficult and debilitating. In 1919 he was awarded the Rothschild Prize, and was appointed 'Lektor' for music theory at the University of Vienna. This was an unpaid appointment, and he had to wait a further year before he had an official position, with a very modest salary, as lecturer for harmony, counterpoint, form and instrumentation at the University, the same position that had once been held by Bruckner. He also increasingly appeared as a performer, especially in chamber music.

A welcome addition to his income, apart from private tuition, was also provided by his work at the Neue Wiener Bühne, a theatre where he was engaged to provide incidental music for the plays. It was here that he met Karl Michael von Levetzow (1871-1945), who was later to write the libretti for all his remaining operas. Gál composed the music to Levetzow's play Ruth, which was performed at the theatre, and this music was later turned into a suite and performed by the Vienna Philharmonic Orchestra, but eventually it was rejected by the composer, and, like so many other works, 'laid aside'. It was not until 1924, when, after the phenomenal success of Die Heilige Ente (see below), he signed an exclusive contract for his compositions with the publisher Simrock, who in turn provided him with a regular income, that his financial situation was really secure.

Nevertheless the cultural upsurge of the twenties in Germany brought a period of rapid advancement for Gál. Publishers wooed him, and there were performances of all his works. He continued to live and work in Vienna, but it was mainly in Germany that he increasingly found opportunities. He frequently travelled there to performances of his works.