On December 16, 2002, Foster was traded, along with Wes Helms, to the Milwaukee Brewers for Ray King.

In 2005, after being picked by the Chicago Cubs in the Rule 5 draft in 2004 and undergoing surgery on a torn labrum, Foster returned to the Braves when his contract was purchased from Triple-A Richmond.

On October 30, 2007, Foster signed a minor league contract with the Kansas City Royals.

In late March 2009 at the end of spring training, Foster retired from professional baseball.

[citation needed] In 2017, Foster became the pitching coach of the Chinatrust Brothers of the Chinese Professional Baseball League.