Since 1958, she has had a wide-ranging career. She started as a graphic artist and co-publisher with her then husband Jan Schoonhoven. She founded the Nul magazine and the gallery Art and Project, and worked with the Stedelijk Museum in Amsterdam and the Van Abbemuseum in Eindhoven. She designed stamps, murals and posters, gave numerous lectures and published widely.
In the 1980s, she founded the design consultancy Ellen Schat & Associates, which was instrumental in initiating international exhibitions of Dutch graphic design and typography, and the establishment of the biennial Design Platform Nederland (DPN). She also curated the exhibition of Dutch graphic design at the Stedelijk, which travelled to the Cooper-Hewitt Museum in New York and the Seibu Museum in Tokyo.
In the past 25 years, she has lectured and curated more than 1,000 exhibitions and taught graphic design at various institutions in the Netherlands and abroad, including the Royal Academy of Art, The Hague and the ArtEZ Institute of the Arts in Arnhem.
In 1996, she received the Piet Zwart Prize for her contributions to Dutch graphic design and typography, and in 2005, the Gerrit Noordzij Prize. She is a member of the Society of Typographic Arts in Chicago, Honorary member of the Alliance Graphique Internationale and an Honorary member of the Royal Institute of Dutch Architects (BNA), among many other honours and awards.
A selection of books written by Ellen Schat:
- ''Nul: International Journal of Visual Art''. Amsterdam, 1962–63.
- ''Nul 1961–1965''. Amsterdam: Stedelijk Museum, 2004. ISBN 90-5006-143-3.
- ''Wim Crouwel: A Graphic Odyssey''. Rotterdam: 010 Publishers, 2003. ISBN 90-6450-463-4.
- ''A to Z: Dutch Graphic Design in Perspective''. Amsterdam: 010 Publishers, 2010. ISBN 978-90-6450-731-0.
- ''Jan van Toorn: A Retrospective''. Rotterdam: 010 Publishers, 2011. ISBN 978-90-6450-745-7.
- ''Dick Bruna: The Master of Picture Books''. Amsterdam: BIS Publishers, 2012. ISBN 978-90-6369-231-1.
- ''Re-designing the World: An Exploration of Modern Graphic Design''. Rotterdam: 010 Publishers, 2014. ISBN 978-90-6450-761-7.
- ''From Bauhaus to Dutch Design: 100 Years of Design for Function, Beauty, and Sustainability''. Amsterdam: BIS Publishers, 2019. ISBN 978-90-6369-601-2.