Kai Allsopp fired the first chance over the bar on 8 minutes from inside the six yard box after a free kick was nodded down into his path.
Allsopp was again in on goal two minutes later after being played in by Jefferson Louis, but he blazed over.
Louis headed a cross towards goal on 12 minutes, but Vincent Angelina was equal to it.
Brentford took the lead with 19 minutes played with a trialist finding the back of the net. Slough appealed in vain for an offside decision in the buildup, but play continued and Byron Wilson’s cross was met by the head of the striker to give Sami Nabbad no chance.
The Bees had a good chance four minutes later after a clearance cannoned off Oscar Lucey, but Romeo Beckham fired over.
Good feet from substitute David Ogbonna led to him getting a shot off from outside the box on 62 minutes, but it was just wide.
Brentford threatened a second goal soon after with another trialist bursting into the box and rounding EDS goalkeeper Ryan North, but Scott Davies made a crucial block in the six yard box.
Ollie Shield got up well to challenge North to a high ball on 72 minutes, but could only head over the bar.
North did well to make another save to keep out a Brentford striker, and late on Tyrese Dyce got up to head a free kick goalwards, but the ball struck the foot of the post.
Davies was unlucky to see a free kick on the edge of the box bit the crossbar not once, but twice – however seconds later Slough were level. A mistake from Brentford’s goalkeeper saw him play the ball straight to substitute Emmanuel Robe, who rolled it into an empty net from around 20 yards.
Slough Town Line up
Sami Nabbad, Oscar Lucey, Leon Chambers-Parillon, Jacob Wilson, Darnell Baxter-Alleyne, Jefferson Louis, Jonny Giles, Scott Davies, Tyrese Dyce, Munashe Sundire, Kai Allsopp. Substitutes: Josh Stranks, Kevin Bilicki, David Ogbonna, Harvey Harry, Josh Oyinsan, Ryan North, Emmanuel Robe.