Grayson said: "We know all about Neill from last season and what he brings to the club.Neill already knows most of the lads here, but we're pleased we've been able to complete the deal before we go to Slovakia on Saturday.
"He has plenty of experience at Championship level and is another important addition to our squad."
Scotland-born Collins began his career Queens Park in 2001 and his other previous clubs include Dumbarton, Sunderland, Hartlepool and Wolves.
Source: PA
Source: PA