Ian Rapoport of NFL Network reported the news. Ealy's signing comes after the team released veteran Bruce Irvin on Saturday.
Ealy began Cowboys camp on pace to make the roster. He was part of the second-string defense on their initial depth chart, ahead of names such as Dorance Armstrong and Charles Tapper. But as camp wore on, Ealy began losing his spot on the team, with Armstrong and Randy Gregory establishing themselves as the backups behind Demarcus Lawrence.
The Raiders will be hoping Ealy shows some pass-rushing skills he's yet to display against NFL competition. He has recorded just 15 sacks in four seasons and never had more than five sacks in a campaign.
Odds are they will try to use him as line depth for now, in much the same way the Jets did a year ago. Dallas experimented with putting Ealy on the inside of the line during camp as well, so it's possible Oakland will look to do something similar.