Gregoire was born in Cape Town in 1909, to the political cartoonist, D.C Boonzaier. Growing up amongst all the art and artist, he was well taught between his father’s friends (Pieter Wenning, Moses Kottler and Anton van Wouw). His father was opposed to formal art training and Gregoire advanced his studies through practicing artist in the Cape.
Gregoire held his first exhibition at age 16, setting up his own studio (against his father’s wishes) in 1932. After a successful exhibition Gregoire financed his own study trip to London (Heatherley’s School of Art, 1935)
Gregoire was also the founding member of the New Group in 1937, also traveling extensively in South Africa, holding exhibitions and teaching.
Gregoire participated, with 43 other SA artists, in the ‘Exhibition of South African Art’ at the Tate Gallery in London in 1948.
In 1959 he was awarded the SA Medal of Honor for Painting by the SA Akademie vir Wetenskap en Kuns and in 1964 the first book on Gregoire and his work, written by Dr F. P. Scott, was published.
Gregoire was a painter of portraits, self portraits, flower studies, still life studies, tree studies, rural landscape scenes and interior scenes in different media (watercolor to oil).
Gregoire passed away on 22 April 2005.
His works are to be found in many significant private and public collections including the South African National Gallery, Cape Town; Johannesburg Art Gallery; Pretoria Art Museum; Durban Art Gallery; Ann Bryant Gallery, East London; William Humphreys Art Gallery, Kimberly; Hester Rupert Art Museum, Graaff-Reinet.