The Belgium international ended a four-game run without a goal when he headed home an Ashley Westwood corner with 10 minutes remaining.
Strike partner Gabriel Agbonlahor hailed Benteke’s impact at Villa Park.
“He’s still only 21 but he doing great for us. He’s helped us with the goal tonight and all credit to him,” said Agbonlahor, skipper for the night.
“It was a scrappy game but we’ll take the three points and move on.”
That feeling was shared by midfielder Barry Bannan, who said: “There’s less expectation against the big clubs and it was hard to come out tonight and win the game but we dug in and got the three points.
“It’s massive. We need to win games and it’s big relief for us. There’s been a lot of people talking about us being in the bottom three and it’s hard to take.
“We’ve got to keep doing what we’re doing and hopefully it’s good enough. We’ve got a great team spirit here, we’re all young lads and we’re learning every day.”
Villa’s third win of the season moved them out of the bottom three in front of their lowest home league gate — 28,692 — for six years.
The game was not a classic but Villa deserved the three points after enjoying the bulk of possession and looking more threatening.
Bent was left out of Lambert’s matchday plans for the second successive game with rookie striker Jordan Bowery again preferred on the bench. Villa denied former Tottenham striker Bent had left the ground after being left out and he watched the game from an executive box.
“Darren Bent just has to play well and train well. I’m not going to invent something that football people understand. He has a future, everybody has,” Lambert insisted afterwards.
Villa, who fielded eight players aged 23 or under, enjoyed the bulk of the possession and the recalled Brett Holman impressed in central midfield.
Reading rarely threatened a Villa back four in which Irish international Ciaran Clark again impressed.
In an uneventful first half, Andreas Weimann squandered a golden chance to break the deadlock on 27 minutes. Benteke created a yard of space inside the box before finding Weimann unmarked at the far side of the six yard box but he fired high over the bar.
The second-half followed a similar pattern, with few goal chances. The game appeared to be heading for a stalemate but with 10 minutes left Benteke settled the issue.
Lambert’s £7m summer signing from Genk climbed above the Royals defence and his downward header flew past Federici.
ASTON VILLA: Guzan, Lowton, Baker, Clark, Stevens (Lichaj 24), Holman (Ireland 67), Westwood, Bannan, Weimann (Albrighton 68), Agbonlahor, Benteke.
READING: Federici, Cummings, Morrison, Mariappa, Shorey, Robson-Kanu (McCleary 83), Leigertwood, Tabb, McAnuff, Roberts (Hunt 79), Le Fondre.
Ref: Lee Probert (Wiltshire).