Maria Litauer studied from 1917 at the Warsaw School of Fine Arts under Stanisław Lentz. From 1920 she studied at the Academy of Fine Arts in Krakow with Wojciech Weiss, whom she considered her master until the end of her life. She continued her artistic education in Berlin. After returning to Poland, she took up studies in the atelier of Tadeusz Pruszkowski. She received her diploma in 1938 on the basis of a set of landscape compositions.

The artist belonged to the milieu centred around the Institute of Art Propaganda, and co-founded the KOLOR group. She took part in the World Exhibition Centennial of Progress, in Chicago, in 1934, in the International Women's Exhibition in Bucharest, and in 1935 she received the Silver Medal at the International Exhibition of Contemporary Art in Brussels. Arrested in 1939, she and her husband, Roman Schneider (a lecturer in applied arts at the pre-war Warsaw Academy of Fine Arts), were deported to a gulag in Mariinsk near Novosibirsk; after the announcement of amnesty, she escaped from the Soviets with the Anders Army. She stayed in Iran, where she and Roman Schneider founded the Polish Artistic Production Company. The artist spent the years 1945-1949 with her husband in Beirut, where she specialised in occasional commissions, taught painting and participated in exhibitions, including at the Museum of Art and the Centre des Etudes Superieures. The Schneiders tried to emigrate to England, but having failed to obtain permission, they came to Canada in 1950.

For a year, Mary taught painting at Acadia University in Wolfeville, Nova Scotia. After settling in Toronto, in 1951, she taught at the Magog Centre summer school, where she also served as director. In 1963, the Schneiders, with a group of artists, founded the Schneiders School of Fine Arts in Actinolite/Ontario, a summer training centre that has been popular with art students of all ages and countries, as well as government recognition and financial support. "Applications are plentiful here that the painting and ceramics course will run all summer. The opening ceremony was held on a large scale. 500 people came down and the opening was done by the Ontario Minister of Tourism and Information" ('The new school of the Schneiders', The Unionist).

In addition to her commitment to teaching, Mary was one of the Polish artists most frequently exhibiting in Canadian galleries, as well as being active in the Polish community. In 1952, two Polish artists, Mary Schneider and Baroness Anna Romer, showed their work in Toronto at the Eaton department store. In 1953, the Canadian National Exhibition (CNE) in Toronto held an exhibition entitled Poles in Canada, where Mary Schneider's work was on display. The artist's painting 'Lebanon', painted in Beirut, was donated to Social Services at the CNE in Toronto. In 1956, a joint exhibition of the Schneider couple was held at Memorial Gardens in Toronto. In 1958, the annual exhibition of the Colour and Form Artists' Society, of which Mary was secretary and had participated in its exhibitions since its foundation, in 1951, took place in Toronto.

In 1960, Mary and Roman Schneider's multiple anniversaries were celebrated at the Polish Literary and Art Club: 25th wedding anniversary, 50th anniversary of Roman Schneider's work and 30th anniversary of Mary's work. In 1961, the Toronto Public Library displayed 40 of Mary's drawings - old Toronto architecture masterfully rendered by the artist in pencil and ink. In 1964, the Art Education Centre hosted an exhibition of the Schneider couple's work. Mary showed oils, watercolours, drawings and monotypes whose main theme was nature and the Canadian landscape, while Roman presented ceramics. Their next joint exhibition was in 1967, at the Pollock Gallery, where Roman showed ceramics and Mary showed watercolours, luminous and colourfully sophisticated: 'the sun on her watercolours warms and the water takes on a life of its own,' wrote Waclaw Iwaniuk poetically ('Związkowiec').

For Canada's 100th anniversary, Mary Schneider presented the mayor of the city with a 'Toronto Portfolio', twelve prints housed in an ornate portfolio, inspired by the city's historic architecture. In 1969, the Schneiders were awarded the Golden Cross of Merit by the Polish Government in Exile for their contribution to Polish culture and the Polish community.

The artist travelled extensively: to Israel, Italy and Mexico, sketching and painting watercolours everywhere. Her subjects were both the architecture of the places she visited and the landscape. In 1970, at the Pollock Gallery, the painter showed watercolours created in Mexico, in 1971 she presented sketches created during her trips to Rome and Jerusalem, and in 1972. - 52 watercolours from all of the artist's journeys, which created a painterly diary of her travels, stunning in its sensitivity and perfection of handling colour, enthusiastically received by Canadian critics. An exhibition of works from the journey was repeated at galleries in Cobourg and Peterborough.

As part of an art festival signed by the Toronto Public Library in 1977, an exhibition - 16 Polish-Canadian Artists - was organised, an opportunity to confront artists of different generations. Mary Schneider exhibited the floral motif 'Trillium'. The exhibition catalogue contained a flattering assessment of the artist's work (by Julius Marosan), emphasising her mastery of colour, the lightness and agility of her line, her realistic and poetic approach to reality.

The artist's works took part in the exhibition Polonia of Tomorrow - Polonia of Tomorrow, organised in 1978 by the KPK in Toronto. Schneider presented her drawings at the Kar Gallery in 1980 and at the Soho Gallery in 1981. The Canadian press recalled the artist's long artistic and life path (Lotty Dempsey - "Artist spent time in Siberian prison" in the Star).

Schneider painted in oil and acrylic techniques, created series of drawings of city architecture, and specialised in watercolour and pastel. Nature, flowers, landscape - these were subjects to which she returned throughout her life. Her colour palette was post-impressionist, saturated with browns, greens, with a light, delicate palette in creating with watercolour.

The artist was a member of the Ontario Society of Artists, the Canadian Society of Painters in Water Colour, the Colour and Form Artists' Society and the informal Mary Schneider Art Club, made up of friends and students of the Schneiders. The Schneiders School of Fine Arts was incorporated into Loyalist College in 1990, which took over the organisation of the summer courses.

Before her death, Mary Schneider created the Roman and Mary Foundation at the Ontario College of Art and Design, which has been awarding $2,000,000 scholarships to OCAD students since 1995, with a preference for a student of Polish descent, as noted in the foundation's documentation.

The artist's works can be found in: Tom Thomson Museum, Art Gallery of Northumberland, Hart House/Toronto, Osgood Hall/Toronto, Sir Stanford Fleming College/Peterborough, Rideau Hall/Ottawa, National Museum in Warsaw, Polish Museum in Rapperswil, Maria and Jerzy Kuncewicz House in Kazimierz Dolny. Private owners of Mary's works include: Elizabeth II, Princess Anne, the family of Pierre E. Trudeau, the artist's family in Poland, Canada and the United States.

Work in catalogue
Mary Schneider, 'Flowers', bottom right signed [Mary Schneider], in the collection of Danuta and Andrzej Pawlowski donated to the Consulate General of the Republic of Poland in Toronto. Flowers were a favourite motif of the artist and often painted by her. "Flowers", in the consulate's collection, is a late work, an oil dating from 1985, when the painter's palette became subdued and the depiction of flowers was a play with colour and shape. Sketchiness became a virtue here, merely suggesting the subject. Lightly painted, scattered on a green flat background, without depth, the pink and sapphire indefinite flowers are coloured spots softly complementing each other. In keeping with the Post-Impressionists - it is not the subject that is most important here, but the way in which it has been translated into colours and shapes.