Prendergast was born in Abertridwr, a mining village in the Aber Valley near Caerphilly in Glamorgan. His father was a Roman Catholic from Wexford, in Ireland who sought work as a coal miner in Maesteg in south Wales after the 1916 Easter Rising.
His older brother (Stewart) and his twin (Paul) attended the local grammar school, but he was sent to the local secondary modern, where his art teacher, Gomer Lewis, recognised his artistic talent. Prendergast moved to the Slade School of Fine Art in 1964, where he studied under Sir William Coldstream, Robyn Denny, Francis Bacon, Jeffrey Camp, and Euan Uglow.
Liverpool 1973, Bangor University 1974, 1979, 1986, Welsh Arts Council Gallery 1975, Llandudno 1982, Durham 1982, Campden Arts Centre 1982, Swansea 1983, Bath 1987; group exhibitions at Tate Gallery 1984, Rocks and Flesh at Norwich Art School Gallery 1985, Ways of Telling 1989, Natural Element 1989, Mixe 1990, Scarborough City Art Gallery 1991 and elsewhere; represented in Group Wales exhibition, Czechoslovakia 1986-1987, Artists in the Parks, Victoria and Albert Museum, London, Experience of Landscape, Arts Council of Great Britain Touring exhibition; communications for Rural Development Body for Wales, National Trust Gardens 1991; painting of Bethesda reproduced in book Green Bridge: Short Stories from Wales; included in book The New Wales.After the death of Sir Kyffin Williams in September 2006, he was recognised as the leading landscape painter in Wales. His tutor was Frank Auerbach. He taught part-time in a school for one year after leaving the Slade, and then studied for a Master"s degree at Reading University with Terry Frost and Claude Rogers.
He taught part-time at Liverpool School of Art until 1974, then at a local school, Ysgol Dyffryn Ogwen, and then at Coleg Menai, but he concentrated more on developing as an artist.
He specialised in paintings of the Penrhyn slate quarry, which he described as "the biggest man-made hole in Europe, like Bruegel"s Tower of Babel, but in reverse", and of Snowdonia. His early works have an Expressionist style, almost Cubist.
He painted similar views from skyscrapers in Manhattan on a visit to New York in 1993. Examples of his paintings are owned by the Contemporary Art Society of Wales, and the Tate Gallery.
Foreign some years his work was shown by Agnew"s gallery in London, culminating in a touring exhibition.
The foreword to the exhibition catalogue was written by Sister Wendy Beckett, who described him as "a superb colourist and a master of form". The Painter"s Quarry, a collection of critical essays on his work, was also published in 2006. A television profile with the same title appeared on BBC2.
Following his death he had two major tribute exhibitions at Martin Tinney Gallery, Cardiff (2014) and Oriel Tegfryn, Menai Bridge (2013) a book, the art of Peter Pendergast was also published, with an essay by Richard Cork.
With support from the County art adviser, Leslie Moore, he won a County art scholarship to study at the Cardiff School of Art in 1962, despite having no formal academic qualifications. He won the Nettleship Prize for Figure Painting in 1967. Prendergast won prizes at the National Eisteddfod in 1975 and 1977.
He was a member of 56 Group Wales from 1982 until his death.
Married Lesley A. Riding in 1967.
