Grammar's sole objective for the rest of the season must now be avoiding relegation after plummeting to ninth place in National 1, only four points ahead of second bottom Kelso.
"It is our form on the road that is letting us down. We have not won away from Rubislaw since we beat Dundee High on the first day of the season. It was very disappointing, although I thought the final score flattered Stewart's Melville," said coach Stuart Corsar.
Playing with a strong wind, the home side capitalised to lead 15-0 thanks to an Andrew Warnock penalty, an unconverted try from Scrum half Fraser Strachan and a second touchdown by full back Ross McCann just before the break, with stand off Warnock adding the conversion.
The Inverleith side extended its lead in 50 minutes when winger Sean Murchie raced over the Grammar line. Warnock was off-target with the conversion but increased his side's lead to 23-0 with a penalty two minutes later.
Grammar rallied with a score in 68 minutes when flanker Chris Jollands crashed over for a try which stand off Alex Hagart converted.
Lock Stuart Smith dived over four minutes later to give the small band of travelling supporters hope. Hagart added the conversion to make it 23-14 and move Grammar within a score of a losing bonus point.
But the Grammar revival was cut short in added time when Stewart's Melville replacement Tom Croy broke out to score, with Warnock's conversion proving the final nail in the Grammar coffin.
The few positives for Grammar included fine performances from Forwards Adrian Hamilton, Tony McGinness and Ali Mackie, while replacement John Poe looked to be one for the future. Even the normally exciting Peceli Nacamavuto had a quiet game by his high standards.
Grammar's next game at home to Jed-Forest now becomes a must-win match if the Rubislaw side is going to break free of the relegation area.
It must hit the ground running against a Borders side bolstered by a 41-26 win against promotion-chasing Marr.
© Jack Nixon
Stewart's Melville: Ross McCann; Neil Bowie, Ali Greig, Sebastian Trotter, Sean Murchie; Andrew Warnock, Fraser Strachan; Willie Aitken, Ruaridh Mitchell, Rhys Morgan; Fraser Morrison, Jamie Berrisford; Hugh Lindsay, Ben Wilson, Adam Howie.
Replacements: Angus Wallace, Thomas Spowart, Tom Croy, Gregor Portus, Angus Rennie.
Aberdeen Grammar: Alex Ratcliffe; Martin McRobbie, Peceli Nacmavuto, Conor Lavery, Jamie Gilmour; Alex Hagart, Sam Knudson; Peter Gillies, Mike Cox, Matthias Schosser; Stuart Smith, Robin Cessford; Chris Jollands, Tony McGinness, Adrian Hamilton.
Replacements: Fergus McKenzie, Matthew Reid, Ali Mackie, Doug Russell, John Poe.