Williams, 24, joined the Cowboys as a second-round pick in the 2018 NFL Draft. The 6-foot-5, 298-pound lineman did not miss a game over the past two seasons. He started all 16 games in 2020 and drew 14 starts in 2021.
He allowed just one sack in 948 snaps last season. Williams was the No. 11 rated guard in the NFL in 2021, according to Pro Football Focus.
The Cowboys offensive line also was the site's top-ranked unit in the league, while the Dolphins' line ranked last.
Guard Robert Hunt started all 17 games last season for the Dolphins. Guard Austin Jackson and tackles Jesse Davis and Liam Eichenberg each started 16 games in 2021. Guards Solomon Kindley and Robert Jones drew two and one start, respectively.
Center Michael Deiter started eight games. Fellow center Greg Mancz earned four starts. Jackson was the team's lowest-rated offensive lineman, while Eichenberg ranked second-worst. Hunt received the best grade from Pro Football Focus, followed by Deiter.
Eichenberg is signed through 2024. Jones, Hunt, Jackson are signed through 2023. The contracts for Davis and Deiter expire after this season.