Hull hoped he might sign a new deal with the club, having offered him fresh terms with them.
McGregor even bagged the club's Player of the Year award after a superb season for the Championship club.
Gerrard said of McGregor: 'He is a vastly experienced goalkeeper who we feel can add to the options available to us now.
"I have played against Allan a number of times in my own career and I know just how fierce a competitor he can be".
McGregor has won 35 caps for Scotland and in his first spell at Rangers he won three league titles, a hat-trick of Scottish Cups and five League Cups.
ANDREW YATES GettyImages
McGregor, who quit the Ibrox outfit six years in the midst of the club's financial meltdown, said: "When the chance came, it was an absolute no-brainer, so I'm buzzing to be back".
The 20-year-old hitman is wanted on a loan to lead the Rangers attack next season and it's claimed that informal talks between himself and Reds' boss Jürgen Klopp have already taken place to establish if a deal could be worked out.
He added: "I started training here when I was 12 years old and it's incredible to be back". You need to win games, no matter who you're playing.
"I need to sit down with Steven and go through every single thing in detail, we're doing everything on the telephone at the moment because he's not here".
The giant striker has a superb scoring record and has notched 16 Premier League goals in the last two seasons despite being consigned to a role as a late substitute for much of that time.
The great internet debate: Yanny or Laurel
How many Laurel fans here huh?" "If you hear Yanny and not Laurel I don't trust you", user Quincy Quarter-Zips tweeted. So, on Wednesday, the Dallas Cowboys made a decision to get in on the action, posting their own " Yanny vs.
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