On-loan Scott Rendell hit the net for the third successive match as Cambridge secured a win at the Recreation Ground.
The Peterborough man's winner came three minutes before the break when he found the bottom corner from 18 yards.
Cambridge keeper Danny Potter kept the home side at bay, saving from Ishmael Welsh and then an Andy Pugh header.
Grays were reduced to 10-men when George Beavan was sent off for violent conduct, while Jon Challinor almost made it two but his shot struck a post.
Tony Dinning was booked on his delayed debut after finally completing his loan move from League Two strugglers Chester City.
Please turn on JavaScript. Media requires JavaScript to play.
Sent Off: Beavan (59).
Booked: Thurgood, Stuart, Dinning.
Cambridge Utd: Potter, Gleeson, Bolland, Hatswell, Tonkin, Reason, Carden, Challinor, Beesley (Willmott 90), Holroyd, Rendell. Subs Not Used: McMahon, Pitt, Coulson, Crow.
Booked: Carden.
Goal: Rendell 42.
Att: 754
Ref: Darren Sheldrake (Midlands).
What are these?
Print Sponsor
Bookmark with:
What are these?