The Raiders announced the signing late Thursday night and said Pryor would participate in his first NFL practice on Friday. Pryor likely will receive roughly $500,000 guaranteed as part of his deal, according to NFL Network insider Jason La Canfora.
The Raiders play their third preseason game Sunday against the New Orleans Saints, but it's extremely unlikely that Pryor would play. The Raiders then will have three practices before the Sept. 2 preseason finale at Seattle.
After that game, Pryor will be ineligible to practice with the Raiders until he serves a five-game suspension.
When he was allowed to enter Monday's supplemental draft, Pryor was handed a suspension by NFL Commissioner Roger Goodell for the same number of games he would have sat out had he returned to Ohio State. Pryor has said he will not appeal the suspension.
Pryor gave up his final season with the Buckeyes after an investigation into the team's memorabilia-for-cash scandal that cost coach Jim Tressel his job.
Pryor is an impressive physical specimen, measuring 6-foot-5 and 232 pounds and being clocked at 4.36 seconds in the 40-yard dash at his pro day last weekend. He's also coming off his best season statistically at Ohio State, throwing for 2,772 yards and 27 touchdowns with 11 interceptions. He ran for 754 yards and four TDs while helping the Buckeyes win the Sugar Bowl.
The Raiders considered drafting a quarterback to groom for the future in April but didn't find the right fit. Now they have Pryor to fill that role.
Oakland currently is without picks in the second, third and fourth rounds in next year's draft. The Raiders traded the 2012 second-round pick along with a 2011 seventh-round selection for third- and fourth-round picks in this past draft to take offensive lineman Joe Barksdale and running back Taiwan Jones. They sent their fourth-round pick a year ago to the Washington Redskins for Campbell.
The Associated Press contributed to this report.