After 27 months as NBC Universal’s top exec overseeing digital media and ad sales, Beth Comstock is ankling to return to her previous post as chief marketing officer for NBC U parent General Electric.

Salil Mehta, NBC U’s newly appointed prexy of business operations, strategy and development, will now oversee the Peacock’s digital media unit. Comstock’s responsibility for ad sales and marketing will be taken over by Mike Pilot, prexy of ad sales and marketing, who will now report to NBC U chief exec Jeff Zucker.

Mehta, who already reported to Zucker, joined NBC U last month from ESPN, where he was exec veep of ESPN Enterprises, spearheading digital and mobile initiatives for the sports cabler.

Jeff Gaspin, prexy and chief operating officer of Universal Television Group, will take on interim responsibility for NBC U’s femme-centric website iVillage.

As part of its announcement on the management realignment, NBC Universal also said it plans to launch a “virtual women’s network” initiative for advertisers that will offer one-stop-shopping for the online and TV ad platforms of NBC U-owned Oxygen, Bravo and iVillage.

Lauren Zalaznick, prexy of the Bravo and Oxygen cablers, will likely take on oversight of iVillage eventually and spearhead the femme-packaged advertising initiative. In the interim, iVillage Properties prexy Deborah Fine will report to Gaspin.

Comstock’s top lieutenant on the digital side, NBC U chief digital officer George Kliavkoff, will now report to Mehta. Alan Wurtzel, NBC U prexy of research, will report to Pilot.

Comstock, who rejoined NBC U in November 2005 and was most recently prexy of integrated media, returns to GE as senior veep and chief marketing officer. A onetime NBC communications exec, Comstock served as GE’s chief marketing officer from 2003-05 prior to her return to the Peacock.

There had been rumblings early on after her relocation to NBC U that Comstock was competing with Zucker in the race to succeed Bob Wright as NBC U chief — a post Zucker secured in February 2007. More recently, there’d been internal speculation at NBC U that Comstock was prepping her exit.

In announcing Comstock’s move, GE chairman-CEO Jeffrey Immelt and Zucker were effusive about her contributions in crafting NBC U’s digital strategy and increasing the digital media unit’s revenue to $1 billion — a mark reached a year earlier than NBC U originally forecast to Wall Street.

“Beth did a great job defining and growing NBC Universal’s digital efforts,” Immelt said in announcing Comstock’s move. “Under Beth’s leadership, NBC U created industry-leading advertising innovations for customers,” he added. “I want her to use the same approach to drive digital excellence across GE.”

Zucker credited Comstock with bringing to the Peacock “a deep understanding of the opportunities presented by the digital revolution” and for being “incredibly effective in guiding us through a huge shift in our company’s mindset.”

In a note sent to NBC U employees Monday, Zucker said “she never stopped coming up with great ideas.”

During Comstock’s tenure as digital boss, NBC U partnered with News Corp. to create Internet vid site Hulu.com, which has been in beta test mode for several months and is expected to go live within a few weeks.

In 2006, Comstock spearheaded the acquisition of iVillage. More recently, she worked the levers of power within GE Finance to create Peacock Equity Fund, which is designed to invest in tech and media venture with potential to mesh with NBC U’s various businesses.

Comstock said she’s proud of her division’s track record in pushing NBC U’s various businesses to focus on customized advertising for blue-chip marketers and content packages aimed at niche market segments, such as femmes, pet owners and health care.

At the outset, Comstock said her biggest challenge was getting senior managers of the newly merged NBC and Universal assets to incorporate digital opportunities into their strategic thinking and planning.

“Our goal was to get digital embedded across NBC Universal, and we’ve done that. We’ve become a digital company,” Comstock said.

As for her decision to move on, Comstock cited the GE management culture of frequently shifting execs into new assignments. She also was eager to return to a fulltime focus on marketing, with particular emphasis on how GE can harness digital media to create new businesses and services.

“I’m a marketer to my core,” she said. “I like the kind of opportunities that allow me to start new things; it’s one of the things the company values in me. They needed me to come (to NBC U) to get things started in digital, and now they need me to come back (to GE) to start a few new things here.”