Zare joined Massachusetts Institute of Technology as an assistant professor in 1965. From 1966 to 1969, he was jointly appointed in the departments of chemistry, physics and astrophysics at JILA at the University of Colorado Boulder.  In 1969 he became a full professor in the department of chemistry at Columbia University. He was named the Higgins Professor of Natural Science at Columbia in 1975.
In 1977 Zare accepted a position as a full professor of chemistry at Stanford University, becoming the Marguerite Blake Wilbur Professor in Natural Science in 1987.  He served as chair of the chemistry department from 2005 to 2011.
Zare  served on the National Science Board (NSB) of the National Science Foundation (NSF) from 1990 to 1996, and was the board's chair from 1994 to 1996.
He was a founding co-editor of the Annual Review of Analytical Chemistry from 2008–2012.
He is a member of the editorial advisory boards of other scientific publications, among them Chemistry World, Angewandte Chemie, Central European Journal of Chemistry, Journal of Separation Sciences and the Chinese Journal of Chromatography.
Zare served on the Physical Sciences jury for the Infosys Prize from 2014 to 2016. 
He is chairman of the board of directors at Annual Reviews, Inc., and serves on the board of directors of The Camille and Henry Dreyfus Foundation.