Harrell was one of six cuts the Packers made.
The move came one day after Young had his most impressive outing since he signed with the Packers a week into training camp. In Friday night's preseason game against the Seattle Seahawks, Young led an 11-play, 80-yard scoring drive that he capped with a 1-yard touchdown pass.
On the drive, Young scrambled twice for 39 yards and showed the kind of athletic ability that made him a first-round draft pick of the Tennessee Titans in 2006. Young played just two series in the 17-10 loss to Seattle but finished 6-of-7 passing for 41 yards and a passer rating of 130.7.
"I think Vince is definitely one of the players who took advantage of his opportunities tonight," Packers coach Mike McCarthy said after the game.
Harrell spent most of the 2010 and 2011 seasons on the Packers' practice squad before winning the backup job last season.
Young, who was signed on Aug. 5, will have one more preseason game to get more familiar with the Packers' playbook. He likely will see significant playing time in Thursday's exhibition finale at Kansas City.
"I'm still not there yet," Young said after Saturday's game. "I'm still taking it one day at a time. It's a lot coming in. I didn't get OTAs or I didn't get a lot of camp in, so it's a lot trying to catch up."
The 30-year-old Young has a 31-19 record as a starter but hasn't played in an NFL regular-season game since the 2011 season with the Philadelphia Eagles. He went to training camp last year with the Buffalo Bills but was released before the preseason ended.
The only other quarterback on the Packers' roster is B.J. Coleman, who spent all of last season on the practice squad and hasn't challenged for the backup job this year.
Information from ESPN NFL Insider Adam Schefter was used in this report.