Schimmel served as the chief curator of The Museum of Contemporary Art, Los Angeles (MOCA), from 1990 until 2012, where he organized numerous exhibitions.
His father, Stuart Schimmel, collected rare books, focusing on forgeries and publications from the Ashendene Press; he was also a member of the Grolier Club.
During his eight-year tenure, he sharpened the museum's focus on contemporary California art, bringing works by John Altoon, John Baldessari, Chris Burden, Vija Celmins, Robert Irwin, Edward Kienholz, David Park, Charles Ray, Allen Ruppersberg, and James Turrell into the permanent collection.
[12] Schimmel's exhibitions for Newport Harbor Art Museum include Action/Precision: The New Direction in New York, 1955–60;[13] The Interpretive Link: Abstract Surrealism into Abstract Expressionism,[14] Works on Paper 1938–48; Flemish Expressions: Twentieth Century Representational Painting;[15] Chris Burden: A Twenty-Year Survey;[16] The Figurative Fifties: New York Figurative Expressionism;[17] Gunther Forg: Painting/Sculpture/Installation;[18] Objectives: The New Sculpture;[19] and Tony Cragg: Sculpture 1975–1990.
Under his leadership, the museum acquired works by artists such as Diane Arbus, John Baldessari, Chris Burden, Marlene Dumas, Robert Gober, Jasper Johns, Mike Kelley, Paul McCarthy, Bruce Nauman, Charles Ray, Jason Rhoades, Nancy Rubins, Edward Ruscha, Franz West[22] and Gregor Schneider.
His 1992 exhibition Helter Skelter: L.A. Art in the 1990s proved to be a “game-changer,” bringing the work of many young Los Angeles artists to international attention for the first time under the umbrella of themes of alienation, dispossession, and violence.
In June 2012, amid highly publicized internal turmoil at the museum, Schimmel resigned from MOCA, finishing work on the exhibition Destroy the Picture: Painting the Void, 1949–1962 as an independent curator.
[27] Also in 2013, Schimmel organized the exhibition Re-View: Onnasch Collection for Hauser & Wirth, which opened in their London galleries and later traveled to their New York location.