CareerBorn to a Jewish family, Baer attended the University of California, Berkeley. He served as the sports director and business manager of KALX, the student-run radio station. As a junior, he negotiated with Oakland Athletics' owner Charlie Finley to make KALX the official radio station of the Athletics for its first 16 games. Baer served as the play-by-play announcer. He graduated from Berkeley with a degree in political science in 1980. He joined the San Francisco Giants as their marketing director that year. He left the Giants to attend Harvard Business School and work for Westinghouse Broadcasting.
Baer returned to the Giants to help form the ownership group that kept the team in San Francisco when an attempt was made to move the franchise to Tampa, Florida in 1992. Other members of the group include Charles Bartlett Johnson, Scott Seligman, Peter Magowan, Philip Halperin, Allan Byer, and David S. Wolff. He succeeded Bill Neukom as the Giants' chief executive officer on January 1, 2012. He was added to the board of directors of the San Jose Giants, the Giants' Minor League Baseball affiliate in the Class A-Advanced California League, in April 2012.
In 1994, Baer established the first benefit by a professional sports team to fight AIDS.