Braintree came closest to opening the scoring with ten minutes gone. The ball broke on the right of Slough's area and a chip to the back post saw the ball headed back across to the centre only for Michael Parkin to fling himself in front of the Braintree forward and get the ball away before Avery cleared for a corner.
Both sides were having good spells of play without really threatening the opposing teams keeper until Slough took the lead through debutant Andy Ballard in the 36th minute. The ball was worked out to the left flank and then inside to Jamie Brooks. He beat his man and cut the ball back along the six yard line to find Ballard who poked home.
The second half was a largely quiet affair and it wasn't until the 75th minute that either side had a clear attempt at goal and when it came it was Braintree who took their chance and levelled the score. A long ball in from the left back was nodded down into the path of Alex Revell who took his shot well from the edge and converted inside Parkin's right hand post.
The two sides exchanged chances with Mark Avery heading over a Leon Woodruffe free kick before a stinging drive from Revell was palmed over by Parkin.
Whilst a draw was looking increasing likely as both sides appeared content with a point, Slough snatched it in injury time. A long throw from Ballard from the right was flicked on and found the run of Michael Alexis at the back post to convert high into the net under pressure to get the Rebels first win of the season.
Braintree Town Line up
Nick Morgan, Billy Burgess, Mark Jones, Ollie Adedeji, Paul Lorraine, Brad Quinton, Chris Wild, Andy Porter, Ricci Crace, Alex Revell, Louis Riddle. Subs: James Baker, Robbie Martin, Steve Good, Chris Lockwood