Berkowitz, the former Ask Jeeves CEO, has been serving as head of InterActiveCorp's search business since the Barry Diller-backed companyfor $1.85 billion last year. His naming comes after Microsoft the Microsoft unit that handles the Windows operating system, Windows Live and MSN.
When it made the reorganization announcement last month, Microsoft temporarily named Senior Vice President David Cole as head of the Online Business Group, though Cole has been scheduled to go on a leave of absence at the end of this month.
A representative of Ask.com, as Ask Jeeves is now known, confirmed the departure of Berkowitz but did not offer further details.
Berkowitz, who starts at Microsoft on May 8, will report to Kevin Johnson, co-president of Microsoft's Platforms and Services division.
In an internal memo on Friday, Johnson credited Berkowitz with orchestrating the turnaround of Ask.com.
"Steve's management experience, deep functional knowledge of the search and Internet space and understanding of both the offline and online publishing worlds make him a great choice to lead the Online Business Group," Johnson said in the memo, which was seen by CNET News.com.
Before taking the reins at Ask Jeeves, Berkowitz was president and COO of IDG books, where he oversaw that company's expansion of its "For Dummies" line.
Cole, meanwhile, will start his leave of absence next month, Johnson said.
Berkowitz's hiring was earlier reported by The Wall Street Journal on its Web site.
CNET News.com's Elinor Mills contributed to this report.