North Berwick have been in good form in East Division 1 - two leagues below their hosts - and in the semi-final in the national shield competition, but they will not have expected such a comprehensive win at Neilson Park.
The visitors were in imperious form from the outset, and gained control of the forward exchanges, while looking dangerous in attack.
And they struck after just four minutes, with full-back Gareth Walker showing good strength to break a tackle and score.
Liam West added the extras to make it 0-7.
Rhodri Thomas’ visiting North Berwick side continued to dominate, and the former Haddington captain was celebrating again inside the first quarter as centre Kyle Hamilton and winger Murray West went over to move the score to 17-0.
It was a poor start for the home side, but they managed to get themselves on the scoreboard when a well-constructed lineout drive saw the ball moved wide in the North Berwick 22 to allow Ewan Chalmers the space to go over for his second try in as many games to make it 5-17.
The visitors responded immediately, with strong carries from Armstrong, Buchanan and Sanderson taking the visitors towards the Reds’ try line, before prop Alan Gallagher crashed over.
West added the extras to make the half-time score 5-24.
North Berwick all-but secured the win just after half-time, and it was the impressive Murray West who crossed twice in five minutes to seal his hat-trick, while brother Liam added one conversion to move the score to 5-36 with just over 15 minutes remaining.
The home side tried to get back into the match, but were dealt a blow when James Ferguson, captain in recent weeks, was forced off with a leg injury, meaning a backline reshuffle to accommodate Nick Bell and Kyle Adams as the new half-back pairing.
They did get on the scoreboard once more, after strong running by returning skipper Garry Cockburn and centre Graeme Dykes gave the Reds field position, Colin Stuart was the man who rounded off the move.
Bell was off the mark with the conversion, and at 36-10 the game was all-but finished as a contest.
And the visitors sealed the win with another try at the end, as hooker Buchanan went over in the corner.
The club are now hoping to return to winning ways in league action, which resumes on the road to Kirkcaldy this weekend.