Amazon, Berkshire Hathaway and J.P. Morgan have found a chief operations officer to run their new health venture.

The group has hired Jack Stoddard, most recently general manager for digital health at Comcast. Previously, he was on the founding team of Accolade, a Comcast Ventures-backed start-up that helps workers manage their health benefits. He was also part of the executive team that created claims processing engine Optum, which was later acquired by UnitedHealth.

"We are very pleased to welcome Jack Stoddard to our team. He will serve as the chief operating officer of the organization going forward," said a spokesperson.

Sources say that Stoddard's first day is Tuesday.

Author and physician Atul Gawande officially started as CEO of the still-unnamed venture in July, where he kicked off the search for a team. The goal of the group is still murky, but J.P. Morgan's Jamie Dimon recently told CNBC that the initiative will likely start small, in a similar manner to Amazon's small-scale operation during its first few years.

The group has previously said it is looking to tackle the problem of rising health care costs for its combined 1.2 million workers. Many employers are finding that their costs are going up every year, but health outcomes are not improving.

Disclosure: Comcast owns NBCUniversal, parent company of CNBC.