Most OU parking lots are free after 6 pm; look for signs at entrances. We recommend the lot south of Goddard Health Center, immediately to the west of Bizzell Library, across Elm St. It is #A15 on the parking map.
There are two churches immediately north of campus on University Ave: a Presbyterian and McFarlin Methodist. Both allow free parking after hours, and are short walks to the Library.
Two large parking garages, one near Catlett Music Hall and one near the Memorial Union, are both easy walks from the Library. At times they charge $1/hour. After hours, they are usually free unless there are special events, in which they may charge a fee.