[3] From 1954, inspired by Che Guevara who said that churches have the potential to transform the social structure of society, Oosterhuis combined his religious position with political activism.

Some of his changes were considered controversial within the Roman Catholic Church especially writing the prayer for agnostics: "Heer, als U bestaat, kom dan onder ons" ("Lord, if You exist, come amongst us").

[9][10] Oosterhuis founded "De Rode Hoed [nl]" ("The Red Hat"), a discussion centre in Amsterdam in 1990, for his student organisation, and was its director until 1998.

[2][5] Walter Meinrad, a German theologian and musicologist, thinks that the songs by Oosterhuis will leave a lasting impression because they serve no fashion but touch existential human conditions and express tensions such as life and death, doubt and insecurities.

[16] In 2002, Queen Beatrix of the Netherlands asked Oosterhuis to deliver the eulogy at the funeral of her husband, Prince-Consort Claus von Amsberg, a longtime personal friend, in the New Church in Delft:[17] Claus and Oosterhuis had first met in 1968 and he visited the royal family regularly.

[16] That same week, the Protestant VU University in Amsterdam granted Oosterhuis an honorary doctorate in theology.

[16] At De Rode Hoed, André van der Louw announced his Social Democratic Renewal Program, an incentive to reform the Labour Party.

Lothar Zenetti translated his "Ik sta voor U in leegte en gemis" to "Ich steh vor dir mit leeren Händen, Herr" (I stand before You with empty hands), which was included in German Protestant and Catholic hymnals.

[6] When the hymnal's second edition was prepared, some feared that his popular songs would be eliminated because of his dissident stance, but all five and a litany were retained.