Bryan Mbeumo gave Brentford the lead midway through the first half, stooping to nod home his 15th goal of the season.
Brentford had won their previous three matches without conceding a goal – including victories over Fulham and WBA since the Championship schedule resumed.
Second-placed West Brom, without a win or a goal in four games, were not due to play until visiting Sheffield Wednesday on Wednesday.
Mid-table Reading had picked up just one point from a possible six post-lockdown, losing 2-1 at Derby on Saturday.
Before kick off, a minute's silence was held as a mark of respect for the three men who died in a stabbing incident in Reading town centre 10 days ago.
Home captain Liam Moore had also laid a wreath in the centre circle.
Brentford made a sluggish start and were unable to make any significant headway in the final third of the pitch.
Sam Baldock had earlier created Reading's first opportunity but drove wastefully wide from 20 yards out.
Brentford gradually eased themselves into the game and were rewarded when going ahead in the 23rd minute.
Another Marcondes corner from the left was headed back at the far post by the unmarked Ethan Pinnock.
Mbeumo nipped in to nod home from close range – on his first start since having to self-isolate after testing positive for coronavirus.
Brentford assumed control until half time, with 23-goal top scorer Ollie Watkins twice shooting wide from decent positions.
Watkins had a third opportunity in the early stages of the second period but again failed to trouble Rafael from distance.
Reading then probed earnestly for the equaliser, mainly through the hard-working efforts of winger Yakou Meite.
But the Brentford defence held firm and keeper David Raya – as per most of the first half – had little to do.
Reading playmaker John Swift could have tested Raya but he dragged a poor shot off target.
Brentford effectively sealed the win in the 64th minute, when Rafael made a fine save but could only parry Dasilva's powerful 25-yard drive.
Dasilva was allowed to follow up on the loose ball to slot in his ninth goal of the campaign.
Substitute Valencia then made it 3-0 near the end with another well-struck Brentford effort from long range that, this time, Rafael was unable to stop.