The news was first reported by NFL Network.
Penn, a longtime left tackle. moved to right tackle last season after the Raiders selected left tackle Kolton Miller in the first round of the 2018 draft. Penn played only four games, however, as he was placed on injured reserve in October with a groin injury.
Penn was selected to two Pro Bowls during his time in Oakland.
He has started 174 of the 178 games he has played in his 12-season career, including seven seasons with the Tampa Bay Buccaneers.
Williams also stayed away from the Redskins’ mandatory minicamp in June over issues with the organization’s medical staff, multiple sources have told ESPN.
He had a growth removed from his head in the offseason, and those close to him have said he was upset with how many years it took for them to address the situation. But one Redskins source said the team made appointments for him over the years that he did not keep.
ESPN’s John Keim contributed to this report.