The Cubs received $950,000 in the deal, a source told ESPN.
LaHair, who was named to the National League All-Star team last season, batted .286 with 14 home runs and 30 RBIs before the All-Star break but fell to .202 with two home runs and 10 RBIs after it.
After losing the first base job to top prospect Anthony Rizzo in June, LaHair was a bench player for the remainder of the season.
An outstanding run producer in six Triple-A seasons through 2011, LaHair is being looked at as a first baseman and designated hitter for the Hawks, who finished third in the Pacific League following back-to-back pennants in 2010 and '11.
Information from ESPN The Magazine's Buster Olney was used in this report.