Foster is an accomplished rabbi emeritus for the Denver Temple Emanuel. Foster marched with Dr. Martin Luther King Jr. from Selma to Montgomery, AL in 1965 and has since spent his life championing civil rights. Foster has created a community that fosters interfaith and race relations, and condemns gun violence and the death penalty. Foster established the Temple Emanuel Preschool and Kindergarten, now the Early Learning Center at Temple Emanuel, as well as the Stepping Stones to a Jewish Me, a support program for interfaith families.

Numerous organizations have recognized Foster's lifelong commitment to improving the world, and some of his awards include the MLK Presidents Award, The Greater Denver Metropolitan Ministerial Alliance (2010), the Jack Shapiro Community Service Award, Jewish Family Service (2013), and the ALLY Award, One Colorado Education Fund (2014).