One exception to this was his play El avión negro ("The Black Plane", 1970), a commentary on exiled populist leader Juan Perón's 1964 attempt to return to Argentina.

His most successful play, La nona represented a turn towards the grotesque in which the protagonist, a hundred-year-old Italian Argentine grandmother, burdens her working-class family with her senile dementia and ravenous appetite.

Refurbishing a former Buenos Aires sparkplug factory into the Picadero Theatre, they premiered their first festival on 28 July 1981, featuring Cossa's Gris de ausencia ("Pale of Absence") among the evening's repertoire.

Cossa's successful adaptation of La nona into a film encouraged him to provide screenplays for his play El arreglo ("The Deal") and No habrá más penas ni olvido ("Dirty Little War") in 1983.

"), a study in frustrating exile, De pies y manos ("On Hands and Feet"), a realist look into the effect of the dictatorship on one family, and Los compadritos ("The Poseurs"), a controversial review of the events surrounding the 1939 sinking of the Graf Spee.