The under-fire Colombian striker has been singled out for criticism after two sloppy showings in Rangers’ opening Europa League qualifier with Macedonians Shkupi.
But the 22-year-old answered his critics in the perfect manner as he grabbed the all-important away goal with his 18th-minute winner at the City Garden Stadium.
Gerrard’s team had to ride their luck at times but the Light Blues held on for their first away triumph in Europe since beating Sporting Lisbon on their way to the 2008 UEFA Cup final.
Morelos had been warned by his boss that he had better rediscover his killer touch or might find himself slipping down his frontline pecking order.
But with Roma loanee Umar Sadiq still not fit enough for action, he was given a reprieve against the Croatians.
Gerrard did make three changes to the side which saw off Shkupi in Skopje last week, though, with loanees Lassana Coulibaly and Ryan Kent handed debuts, while Ovie Ejaria came in for his first start.
Gerrard was worried by his side’s lack of cutting edge in the previous round and was given more cause for concern as an Osijek side who beat PSV Eindhoven home and away last term sliced through Rangers three times within the opening 15 minutes.
Mirko Maric flashed over Allan McGregor’s crossbar before the Scotland goalkeeper had to scramble away a deflected Alen Grgic effort, with Maric then getting his angles wrong as he connected with a fantastic first-time ball from his skipper Borna Barisic.
But having survived that early storm, Rangers hit their hosts with a sucker-punch.
Croatia international Nikola Katic was determined to impress on his return home and sent Kent racing in behind with a fantastic ball over the top. The winger drove inside but saw his shot nudged wide by a flailing leg.
From the corner, the ball was knocked back to James Tavernier and the Rangers captain produced a trademark cross to pick-out Morelos, who did brilliantly to hold off Danijel Loncar before nodding home from close range.
Osijek’s threat had not been blunted though. Jon Flanagan almost put Rangers in trouble on the half-hour mark as his scuffed clearance fell to Robert Mudrazija 18 yards out but McGregor rescued the left-back, while Tavernier had to boot Petar Bockaj’s strike off his line at the start of the second period.
The Croats were lucky to keep 11 men on the park as Domagoj Pusic escaped with only a yellow after a dangerous airborne collision with Ryan Jack.
McGregor again proved his importance to Rangers as he pulled off another crucial block when Tavernier made a mess of a clearance.
And while Osijek tried to put on the squeeze in the final stages, Gerrard’s team held firm to preserve their vital lead ahead of next Thursday’s Glasgow return.