Per Michael Gehlken of the San Diego Union-Tribune, Chargers general manager Tom Telesco announced McCoy's extension adds one year to his current deal and runs through 2017.
The Chargers had already let it be known they were retaining McCoy despite finishing last in the AFC West.
Per the Chargers' official Twitter account, Telesco said McCoy is "somebody we want to build around."
The team parted ways with six assistants after the season, including offensive coordinator Frank Reich, offensive line coach Joe D'Alessandris, tight ends coach Pete Metzelaars, wide receivers coach Fred Graves, defensive line coach Don Johnson and assistant offensive line coach Andrew Dees.
Telesco said he "wouldn't be opposed" to McCoy's calling plays for the offense but will leave the final decision to his head coach.
McCoy does have an extensive resume as an offensive coach, including serving as Denver's offensive coordinator for three years before the Chargers hired him in 2013.
Despite posting the franchise's worst record since 2003, the Chargers are in position for a quick turnaround. Philip Rivers threw for nearly 4,800 yards with 29 touchdowns. Keenan Allen will return from injury to boost the receiving corps.
The Chargers do lose receiver Malcom Floyd to retirement and face a big decision regarding free-agent tight end Antonio Gates, but McCoy has a solid offensive nucleus to work with to get the team back in the playoff hunt in 2016.