In the face of the post-merger transformation afoot at NBC Universal, Angela Bromstad decided Thursday that the time was right to make a graceful exit from her post as prexy of primetime entertainment for NBC and Universal Media Studios.

Bromstad disclosed her decision to her staff Thursday afternoon, as first reported by Variety. Her future at the Peacock had been uncertain since late last year, after incoming NBC Universal CEO Steve Burke recruited former Showtime entertainment topper Robert Greenblatt to oversee all programming, production and marketing as chairman of NBC Entertainment.

“I cannot possibly sum up my thoughts and emotions in an email, but suffice it to say I have tremendous respect for the company and for the people with whom I have had the privilege to work with and know during my time here,” Bromstad wrote in an email to her staff. “I take great memories and friendships with me, and I wish you all the best going forward.”

Bromstad declined further comment.

The exec transition comes at a tricky time for NBC as the network is in the thick of making pilot pickup decisions for the 2011-12 season. On Wednesday evening, Bromstad gave the go-ahead to an ambitious supernatural police drama, “17th Precinct,” from “Battlestar Galactica” exec producer Ron Moore.

But with a new regime and a new owner, Comcast, taking the reins, Bromstad likely surmised that her presence, even on a short-term basis, could make things awkward for Greenblatt as he settles into the job, which is broader in scope than Bromstad’s post.

Bromstad had been with the Peacock since 1994, signing on as director of movies and miniseries. She rose steadily through the programming ranks, shifting between the network and studio sides. Among the shows she championed during her tenure were “Community,” “Parenthood,” “The Office,” “Friday Night Lights,” “30 Rock,” “Las Vegas” and “Crossing Jordan.”

Bromstad left the domestic NBC fold in mid-2007, after Ben Silverman was ushered into the Peacock and relocated to London to serve as prexy of international production for NBC Universal Television. She accelerated NBC U’s push into local production and steered the acquisition of British production powerhouse Carnival. She returned to Universal City in late 2008 as prexy of primetime entertainment for the network and its UMS studio arm as it became clear that Silverman’s tenure at NBC Entertainment would be short.

Bromstad never fielded a runaway hit for the Peacock, but she is respected in the creative community.

“She was a huge supporter of both ‘Parenthood’ and ‘Friday Night Lights.’ I found her to be a super-intelligent and passionate executive,” said “Parenthood” and “FNL” exec producer Jason Katims. “The message she was always sending to me and everyone on ‘Parenthood’ was how much she cared about the show. She really got behind it. All of her notes helped the show be the best of what it could be. It was something we were both on the same page about: to make it great.”

(Stuart Levine contributed to this report.)