A nationalist, he was prominent member of the Esquerra Republicana de Catalunya (ERC, Republican Left of Catalonia).

[2] In 1916 the Cultural Council of the City of Barcelona was established and Gassol was given a position in the office of Educational Technical Assistance.

[2] Gassol began to contribute to magazines and won local awards for his poetry, which was published in his first collection in 1917, Àmfora.

In 1921 he staged a dramatic poem in three acts, La cançó del vell Cabrés (Song of the Old Goat).

In 1924 Gassol was threatened with jail and fled to France, where he became acquainted with Francesc Macià, the future president of Catalonia.

In 1926 he was one of the ringleaders of the Prats de Molló plot, where a group of militants attempted to launch an invasion from French territory.

[2] In 1928 Grassol and Macià visited Uruguay, Argentina, Chile, New York and Cuba, where they helped draft the Interim Constitution of the Catalan Republic.

[1] In Havana he participated in creating the Partit Separatista Revolucionari Català (Catalan Revolutionary Separatist Party).

He returned to Belgium and in 1929 was living in Brussels, where he founded, helped by other exiles (especially Francesc Macià i Llussà), the Casal Català de Brussel·les.

[3][2] After the end of the dictatorship of Primo de Rivera in 1930 Gassol spent a few days in the Figueres prison and then was allowed to return to Barcelona.

[2] During the events of 6 October 1934 President Lluís Companys proclaimed the Catalan State within the Spanish Federal Republic.

[1] During the first months of the Spanish Civil War (1936–39) Ventura Gassol tried to ensure the safety of various threatened people and to preserve religious monuments.