Changing the way it does business, Medicare on Friday unveiled a far-reaching overhaul of how it pays doctors and other clinicians.

The goal is to reward quality, penalize poor performance and avoid paying piecemeal for services for the program’s 57 million elderly and disabled beneficiaries. Whether it succeeds or fails, it is one of the biggest changes in Medicare’s 50-year history.

The complex regulation, nearly 2,400 pages long, is meant to carry out bipartisan legislation passed by Congress last year. Its full implementation will take years.

Some clinicians have questioned whether the new system will force small practices and solo doctors to join big groups. On Friday, the Obama administration sought to calm their concerns.

“Transforming something of this size is something we have focused on with great care,” said Andy Slavitt, head of the Centers for Medicare and Medicaid Services.

Officials said they considered more than 4,000 formal comments and held meetings around the country attended by more than 100,000 people. The final rule eases some draft timelines and gives doctors more ways to comply.

Sen. Orrin G. Hatch (R-Utah), chairman of a panel that oversees Medicare, called it an “important step forward.” The American Medical Association said its first look suggests the administration “has been responsive” to many points doctors raised.

The Medicare Access and CHIP Reauthorization Act creates two payment tracks for clinicians. It affects more than 600,000 doctors, nurse practitioners, physician assistants and therapists, a majority of the clinicians billing Medicare.

Starting in 2019, they can earn higher reimbursements by learning new ways of doing business and signing on to what’s called “alternative payment models.” In those, clinicians agree to accept financial risk and reward for performance, report quality measures to the government and use electronic medical records.