The Cougars were disappointing and never looked like registering a score.
Three first-half tries had them on the back foot, with a further two in the second from the league’s form side adding to the pain.
Keighley ran the league-leaders close in March, losing by just two points, but were unable to show the same desire in a hapless first half.
The Centurions barely created any clear-cut chances, but somehow found themselves 18 points up going into the break.
Tom Armstrong’s line break and dummy put Leigh ahead after 12 minutes.
A real lack of attacking flair, coupled with many sloppy mistakes from both sides, will have added to the frustration of player-coach Paul March, as his side conceded two more soft tries.
Bob Beswick and Oliver Wilkes barely had to break sweat in adding another two tries, with Keighley showing signs of fatigue after a long, hard season.
It did not get any better in the second half, with both sides contributing to a drab match.
Greg McNally and Martyn Ridyard put the icing on the cake, with both scoring without much effort needed.
The Cougars are far from out of the running for a play-off place but will need to improve as they approach the crunch part of their season.
Leigh Centurions: McNally, Higson, Pitman, Armstrong, Kay, Ridyard, Brierley; Wilkes, Beswick, Emmitt, Sarsfield, Haggerty, Barlow. Substitutes: Penkywicz, Aspinwall, Hopkins, Acton.
Keighley Cougars: Craven, Barnett, Lowton, Haley, White, Jones, March; Shickell, Feather, Hesketh, Pursglove, Rawlins, Lindsay. Substitutes: Lynam, Sagar, Law, Cherryholme.
Referee: A Gill.