Despite an underwhelming first-half showing, Manchester United's quality saw them through in the second-half as they ended their two-game winless run in the league against a nonetheless vivacious Brentford side.
Truth be told, David de Gea kept the visitors in the contest before the break thanks to a string of fantastic saves, but it was goals from Anthony Elanga, Mason Greenwood and Marcus Rashford — three academy graduates — that ultimately earned them the three points.
Ivan Toney scored a late consolation for the Bees to take his goal tally for the season to five.
The result sees both sides remain in their respective positions on goal difference, with Brentford still comfortably above the relegation dogfight in 14th and Manchester United piling the pressure on in the race for European football from 7th.
Story of the game
Coming into the match, Brentford head coach made three changes to the side which was defeated by Liverpool at the weekend, the most notable of which saw Jonas Lossl make his league debut for the bees at Alvaro Fernandez's expense.
After some good early pressure out of possession, Brentford earned themselves an early break when Bryan Mbeumo teed up Mathias Jensen on the edge of the area, but the Dane failed to direct his effort on target on the half-volley.
Still, what that early chance demonstrated was that Rangnick's side wouldn't have a second to spare on the ball against a team that love to press just as much as they do.
Having dominated possession from the outset, United's first chance of the match nearly came when Elanga's header across the box was problematic enough to cause a mix-up between Lossl and Bees skipper Pontus Jansson, nearly granting Ronaldo a tap-in, but Sergi Canos was on hand to clear in the nick of time.
Then, within the space of about two minutes, a handful of gilt-edged chances fell the way of the visibly buoyant hosts.
First, Jensen was played one-on-one with de Gea after some superb build-up, but the finish was tame. Brentford recycled possession to work another opportunity for Vitaly Janelt from just inside the area, but Fred got a crucial block in to deflect it behind.
The hosts had conjured a number of chances but United, for their own part, were really struggling to break Brentford down in the earlier stages of the match, hard-pressed in particular getting the ball to Ronaldo in dangerous positions. Their frustration was manifest when Diogo Dalot took aim from about 30 yards out — it was a remarkably good effort from such a distance, whistling just wide of the near post.
There can be no doubt about it: Brentford were having the better of this contest in the first-half, and by some distance too. They should have scored again when a devastating counter-attack saw Ivan Toney deal Jensen his second one-on-one with de Gea but the goalkeeper was again equal to the eventual shot.
Would the Bees come to regret these missed chances? Not to take anything away from what was proving to be an outstanding display of goalkeeping from de Gea, but at least one of them should have hit the back of the net by half-time — yet the game remained scoreless heading into the break.
United had barely tested Lossl at all in the first-half but they conjured the first notable one of there second: Bruni Fernandes lifted a sumptuous cross into the area which caught the on-loan goalkeeper in no-man's land and met the head of Ronaldo at the back post — the forward's header looked surely destined for goal, but it bounced off the crossbar much to the hosts' relief.
Straight down the other end, Mbeumo was the spearhead for another brilliant breakaway from Brentford and the Frenchman again thread Jensen through on goal but, once more, the final de Gea-shaped obstacle proved too much for the Bees to overcome.
There was only one team that deserved to take the lead on the 55th minute, and it wasn't that which eventually got it. Yes, United found themselves ahead when Fred played a brilliant pass over the Brentford defence latched onto by Elanga who scooped the ball up to catch Lossl off-guard before heading into a virtually empty net.
That moment would prove to spark the otherwise mediocre visitors into life — Lossl was called into action again just moments later when McTominay unleashed a swerving low effort fro range, forcing him into a deceptively awkward save.
United went two goals to the good just eight minutes after opening the scoring. A brilliant knock-down from Ronaldo set Fernandes free in behind the Brentford defence, but instead of taking the shot on himself the midfielder squared it for Greenwood who couldn't miss on the six yard box.
One eight-minute double salvo later and the picture was suddenly a whole lot rosier for Rangnick's side and their travelling support; United's sheer quality had taken its time to show but, after riding their luck a little, they got there in the end.
Brentford nearly clawed a goal back when substitute Rico Henry did brilliantly to wriggle to the by-line and cut it back for Toney waiting in the middle, but the striker's effort was again saved by the feet of de Gea. Mads Roerslev was granted a second bite at the cherry but it blazed high and wide of the target.
And the Bees were made to pay for their profligacy once more when Fernandes drove United forward and played Rashford through on goal, the forward making no mistake from just inside the box with a delightful finish at the near post giving Lossl no chance.
Game, set and match to the visitors, who should have been behind at half-time, but who also more than merited the three points based on their second-half showing alone.
A comeback seemed unlikely now, but there was however time for a Brentford consolation as Toney prodded home following pin-ball in the United box — that goal will do the striker's confident the world of good having failed to find the net since November.
But this was United's evening, with Rangnick and his men securing a vital win after two disappointing results on the bounce.
Takeaways from the match
Profligacy proves detrimental for Brentford
Jensen had a couple of gilt-edged opportunities to put his side ahead in the first-half and another after the break; Brentford's downfall tonight was that they were only able to surpass de Gea after going three goals behind.
For all that the Bees are having a thoroughly enjoyable maiden Premier League campaign, they are still struggling to get the best out of arch marksman Toney — perhaps if he'd been on the end of the chances created, he and Brentford might have scored more than the one goal tonight.
United's quality shines through in the end
It was a thoroughly mediocre first-half display from Rangnick's men, but they pulled it together after the break, scoring a handful of really well worked goals reflecting the innate quality of their squad — even with Ronaldo misfiring.
Elanga's strike was particularly impressive, the forward showing extraordinary guile and composure for someone at just 19 years of age.
Brentford: Lossl; Pinnock, Jansson [c], Bech; Roerslev, Jensen (Wissa 66'), Norgaard, Janelt (Baptiste 62'), Canos (Henry 62'); Mbeumo, Toney.
Unused subs: Fernandez, Stevens, Ajer, Bidstrup, Ghoddos, Forss.
Manchester United: de Gea; Dalot, Lindelof, Varane, Telles; McTominay (Matic 84'), Fred; Greenwood (Rashford 71'), Fernandes [c], Elanga; Ronaldo (Maguire 71').
Unused subs: Heaton, Henderson, Jones, van de Beek, Mata, Martial.
Referee: Andre Marriner
Following defeat here, Brentford are back at home on Saturday as Wolverhampton Wanderers visit west London.