The visitors started slowly and conceded an early opener as Aquile Smith crossed on the left, Jack Jolly with a fine touchline conversion.
Ill-disciplined Rams coughed up five penalties in the opening nine minutes as they let Moseley take control, Willo Bicknell yellow carded before Elliott Creed went over.
Jolly extended the lead, yet the Berkshire side suddenly burst into life at the start of the second quarter.
And they halved the deficit as Mike Cooke’s delicate chip from inside his own 22 was collected by Andrew Lamb, the full back freeing Zach Clow for a superb finish on the left.
Cooke landed a fine kick, but Rams again invited pressure on themselves before Callum Allen barged over from close range for a converted score.
There were no further points before the break, but Birmingham sealed their bonus-point early in the second half, Allen with a rinse-and-repeat effort before Jolly maintained his perfect record from the tee.
Rams flip the switch
Yet out of nowhere the game turned on its head.
Firstly Cooke set-up Rowan Grundy to throw a dummy and glide over, the fightback furthered as captain Max Hayman powered over out wide.
Lamb struck a majestic conversion, and with Rams gaining a strong advantage at scrum time, they cut the gap to four points when Bicknell bullocked over from five metres out.
The momentum was now well and truly with the away side, and they were camped in the Moseley 22 with the lead there for the taking as Jolly was sin-binned.
However, the wily hosts conceded a free-kick from a five-metre scrum, then stopped Bicknell’s charge in a tide-turner.
And in a cagey final 10 minutes, Rams were unable to fashion a clear-cut chance to snatch glory, Moseley substitute Tommy Taylor landing a penalty following a high tackle with a minute to play.
The visitors had one final chance to grab a draw, but Lamb’s attempted kick to touch fell just the wrong side of the try line, full time called as Rams had to settle for a brace of bonus points.
Defeat leaves Seb Reynolds’ side sixth in the table ahead of a week off.
They then return to Old Bath Road to host Clifton on Saturday, February 14.
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