Joseph Allen McDonald (born January 1, 1942 in Washington, DC) was the leader and lead singer of the 1960s psychedelic rock group Country Joe & the Fish.
from Joe's biography on countryjoe.com :
. . . from 1975 through 1979, he became acutely aware of various ecological issues and began to support most animal rights organizations, performing at benefits worldwide in support of their efforts.
The 'Timeline' on the same site, referring to touring in Germany in May 1983:
. . . All craziness, no vegetarian food
The page about ecology and animals has a link to PETA. However Joe's website never specifically states that he is vegetarian or vegan, and there is no other confirmation online.