The controversial policy had led to the release of some inmates just weeks after their imprisonment.
Quinn, a Democrat, announced that all prisoners will have to serve at least 61 days before they can begin earning good-behavior credits toward early release.
He said he did not approve of Department of Corrections Director Michael Randle's decision this year to speed the release of prisoners. But the governor said he won't fire Randle.
"I did not approve the acceleration. I think it was bad judgment to do it," Quinn said. "I have told him in no uncertain terms this was a big mistake."
Corrections officials reported Randle's decision resulted in 1,781 inmates leaving prison early between Sept. 16 and Dec. 14.
Quinn laid some of the blame for the decision on a tight state budget and noted Randle was trying to save money after lawmakers rejected a proposed income tax increase.
In a statement, Randle acknowledged "mistakes in judgment made during the planning" and added, "I take responsibility for this."