It is understood the Baggies are in advanced negotiations for a season-long loan deal for the much-coveted Collyer, 21. It has been suggested there has been no shortage of Championship interest in the United youngster with as many as a dozen enquiries.
Collyer, 21, is regarded as a bright talent at Old Trafford and has already clocked up 13 senior appearances for United.
He only made his move to United's academy from boyhood club Brighton in 2022 and made his senior debut 12 months ago in the Community Shield final against Manchester City at Wembley.
From there he appeared on a further 12 occasions last season, six as a substitute in the Premier League, with starts coming in the EFL Cup and Europa League.
Ryan Mason was keen to bolster his midfield options at The Hawthorns with just three senior options in Alex Mowatt, Jayson Molumby and Ousmane Diakite.
The Baggies' late window business is cranking up with Collyer and Blues defender Bielik set to become new signings number four and five of the summer.
The moves come off the back of Torbjorn Heggem's exit to Bologna in a move worth £10million, which is soon to be confirmed.
Albion were in need of extra options in both defence and midfield.
Collyer, who is an England under-20 international, reportedly had loan enquiries from a dozen Championship clubs. Hull City were among those with boss Sergej Jakirovic saying this week the Tigers were waiting for an answer in the coming days.
The United prospect is seen as a dynamic and energetic midfield player who also has ability with the ball.
There are around two-and-a-half weeks of the summer transfer window remaining before clubs finish business at 7pm on September 1.