Slough made some changes to their line up from the side that had performed admirably at Margate with Darron Wilkinson and Alex Gibson coming into the starting eleven in place of Michael Alexis and Adam Wallace.
In an evenly contested opening ten minutes, the away side opened the scoring with a great finish from Nigel Brake. The ball had been cleared by Jamie Jarvis from a long throw from the visitors, but it was fed back in, flicked onto the back post and Brake acrobatically volleyed the ball into the bottom corner under pressure from Steve Dell.
This buoyed the visitors and they enjoyed a good spell of pressure over the Rebels. Jamie Taylor saw his effort saved by Kieron Drake having run through onto an inadvertant pass from Carl Rook and having rounded the challenge from Marc Leach.
The away side had the ball in the net again as Taylor had followed in on an excellent Drake save from a long range drive to finish well across the goal, but the linesman raised his flag and the goal was ruled out.
Drake again had to be alert to tip over a goalbound effort from his own defender, as Jarvis headed down into the ground but at his own goal and Drake tipped over.
Slough's best chance of the half fell to Leigh Mason. Slough worked the ball well down the right to put Gareth McCleary into space. His cross sat up nicely for Mason to head the ball, but the midfielder could not direct his effort on target and it flew past the far post with Gareth Williams stranded.
Slough started the second half brightly with McCleary again looking their best attacking outlet. The forward played into Anaclet Odhiambo who finished well past Williams but was caught offside and the goal was ruled out.
McCleary tested Williams with an effort of his own with a low drive having moved upfield with the ball but it was Horsham who got the next goal despite Slough's bright start to the half.
Lewis Taylor received the ball on the edge of the area and just about got round the challenge of Marc Leach. As the ball didn't travel forward with the full back, Rook was running in as the ball had positioned itself perfectly for his run and he finished with the outside of his foot from just outside the six yard box.
Odhiambo twisted and turned past his marker and fired the ball across the goal for a corner. Matt Glynn floated into the back post, it was headed back over and Jarvis helped it over the line to give the Rebels a lifeline.
The hope only lasted a few minutes as John Westcott quickly restored Horsham's two goal advantage. Taylor ran in behind the defence on the left and fed the ball across the face of goal into the path of Westcott on the opposite side and the midfielder finished well under pressure from both Drake and Jarvis.
Taylor lashed over when well placed on teh edge of the area as the advantage should have been increased and Glynn, following a great weaving run, shot wide and Woodruffe followed with a similar effort soon after.
Horsham though looked comfortable in the closing stages and picked up only their third win "at" Slough.
Horsham Line up
Garath Williams, Lewis Taylor, Ian Payne, Eddie French (c), Tom Graves, Andy Walker, Lee Carney, John Westcott, Jamie Taylor, Carl Rook, Nigel Brake. Subs: Andy Howard, Matt Geard, James Cant, Kieran Johnson, Alan Mansfield.