UPDATE: Les Moonves has just released a statement on the exit of Amy Baer from CBS Films: “We thank Amy for her important role in building CBS Films. Going forward, we remain fully committed to the division’s focus on a targeted slate of smart acquisitions and quality homegrown productions in all genres. CBS Films is small in the overall size and scope of our company, but continues to fit nicely with the Corporation’s premium content strategy. We’re excited about its future and to start its next chapter.”

EXCLUSIVE, 2:57 PM: Amy Baer will transition out of the post of president and CEO of CBS Films, ending her four-year tenure at the start-up production/distribution company in late October. Baer will immediately join Laurence Mark as producer of the Jon Turteltaub-directed Last Vegas, CBS Films’ Dan Fogelman-scripted comedy that revolves around four best friends in their late 60s who decide to escape retirement and throw a Las Vegas bachelor party for the only one of them who stayed single.

Baer confirmed her exit to me just now, and said that it came after two months of discussion with CBS chief Les Moonves. CBS Films has been his baby, and Baer said that with the focus switching to acquisitions — CBS Films made the biggest deal of the 2011 Toronto Film Festival when it acquired the Lasse Hallstrom-directed Salmon Fishing In The Yemen for north of $5 million — it seemed a good time for Baer to move on and focus on the kinds of mid-budget movies she likes most. She sparked to jumping in as producer but would not rule out a return as an executive. Before launching CBS Films, she spent 17 years as an executive at Sony Pictures.

The CBS Films structure might change somewhat, but Wolfgang Hammer continues to be COO, with Scott Shooman is head of acquisitions, Steven Friedlander head of distribution and Terry Press continuing as marketing consultant. How Baer is replaced to generate in-house productions will be worked out soon.

“This has been an amazing experience,” she said. “How many people get to start a distribution company from scratch? It’s not something I ever could have done at Sony, as much as I loved the people there. Leslie has been great to work with, but as this evolved with acquisitions a bigger piece of what we’re doing, I just felt like following my heart, which is making mid-range studio films. That was and continues to be my forte.” Baer said that was reinforced when she attended the premiere of Moneyball, a book she brought in while she was an executive at Sony Pictures and supervised hits that included My Best Friend’s Wedding.

CBS Films’ performance has had its growing pains. The division got out of the gate slowly with the medical drama Extraordinary Measures, which starred Harrison Ford and Brendan Fraser and didn’t perform at the box office. Baer said she felt that the company’s high profile shone an unfair light on a company that needed to build both a production and distribution infrastructure. “The bottom line was, our second release, The Back-Up Plan, grossed $80 million worldwide and was a success, and we got no credit for it, or for casting Melissa McCarthy before she was even on her CBS show Mike & Molly,” Baer said. “Faster was a very successful DVD title, and Beastly was a little gem we spent very little to market, compared to how it did at the domestic box office and on home video. We went from nothing and ran smack into the writers’ strike, and when you are building a distribution company, there will always be hiccups. We have a great team now and I’m proud of where the company is going.”

Besides Last Vegas, CBS Films has several projects nearly ready to start production. That includes the adaptation of the Vince Flynn bestseller American Assassin, which Ed Zwick is directing and casting. The supernatural thriller 7500 will begin shooting in late October, and the division is looking for a director on Hellfest.

Acquisitions will continue to be a priority for CBS Films, which started in that direction with the remake The Mechanic and has become an aggressive player for finished films that can play in wide release.