Johnson signed with the Raiders on Monday, Michael Gehlken of the Las Vegas Review-Journal reports.
A 2008 fifth-round pick, Johnson has bounced around the league as a third-string quarterback for most of his career, last attempting a pass in a regular-season game in 2011. He lost out to Geno Smith in a battle for the Giants' No. 2 job last preseason, and then caught on with the Texans for part of November and December. Johnson may get the chance to compete with 2016 fourth-round pick Connor Cook for the backup job in Oakland, though the team also figures to add another veteran and/or draft pick. Johnson is an Oakland native and cousin of Marshawn Lynch.