Galway native Maurice Callanan struck five second-half points to deny his own county men as Robert Emmetts edged past Moycullen at Ruislip.
The Ardrahan forward hit three successive points shortly after the restart to put the London champions back in front, and he fired over a wonderful score with the last puck of the game to kill off the visitors.
It was all square at half-time, 1-5 apiece, with Callanan's trio of points then putting Emmetts in control.
Vinnie Faherty set up a tense finish when he flicked to the net, but Callanan settled matters to book a semi-final date with Carlow's Mount Leinster Rangers.
Scorers -- Robert Emmetts: M Callanan 0-5 (2f), P Atkinson 0-4, E Brennan 1-1, S Ryan 0-2. Moycullen: V Faherty 1-1, E Noone 0-3 (2f, 1 '65), Philip Lydon 1-0, Pat Lydon, D Kelly, N Mannion 0-1 each.
Robert Emmetts -- N Higgins; J Anderson, E Walsh, B Healy; N Healy, P Horkan, G Hill; K Bolger, M Walsh; B Ennis, A Fitzgerald, S Ryan; P Atkinson, E Brennan, M Callanan. Subs: D McCormack for Ennis (51), K McMullan for Ryan (55).
Moycullen -- M Darcy; S McDermott, M Donoghue, B Faherty; T Higgins, M Lydon, S O Fatharta; E Noone, Pat Lydon; D Kelly, V Faherty, N Mannion; C Bohan, Philip Lydon, C Hurney. Subs: M Darcy for Bohan (52), S Conneely for Philip Lydon (55), R Devaney for Faherty (60).
Ref -- S Cleere (Kilkenny)
Robert Emmetts 1-12, Moycullen 2-7