United icon Beckham played with Moyes at Preston North End.
Beckham told Sky Sports: "I'm sure he has had lot of mentoring, he is one of those managers that has always picked up the phone and spoken to Sir Alex.
"It was always going to be difficult job for whoever succeeded Sir Alex because of what the manager has brought to Manchester United, what he has brought to the game.
"But the same players are there and I'm sure a few more will be added over the next few weeks. Being manager of Man United is a great job."