The visitors led 1-0 at half-time at Harlaw Park against their fellow title contenders thanks to Aiden Combe’s goal in the 41st minute.
After a great piece of opportunism from Scott Barbour - who robbed Locos’ Greg Mitchell before squaring the ball – Combe netted a right footed effort from four yards to set Fraserburgh on their way to another three points.
The league leaders didn’t have things all their own way as Broch keeper Paul Leask had to deny Locos’ Kieran Shanks on three occasions.
And Leask made a brave block to thwart Neil Gauld before West blocked Sam Burnett’s follow-up, before Broch’s Sean Butcher headed against the top of the bar.
The hosts’ cause wasn’t helped on 69 minutes when they had Jamie Michie sent off for a second booking.
And Barbour – the man who set up Broch’s opener – completed a fine day for him on a personal level by scoring the clinching second goal in the 90th minute.
After Ross Aitken’s long ball forward, Barbour sent a fine left footed shot into the bottom right corner of the net with his left foot.
The resultant 2-0 win for Broch puts them onto 52 points from 19 games, with nearest challengers Buckie Thistle on 46 points from the same number of matches.
Saturday’s loss was a major blow for Locos’ title hopes as they are now down in fifth spot with 44 points from 21 league fixtures.
Meanwhile, Fraserburgh's local rivals Formartine United were defeated 4-0 at Buckie Thistle last weekend.
After first half goals for Thistle by Sam Urquhart and Max Barry, the hosts sealed the deal with second half strikes by Marcus Goodall and Andrew Macaskill.
The defeat leaves Formartine sixth in the current Highland League standings with 42 points from 21 games.
There is a busy programme of Highland League fixtures pencilled in for this Saturday, January 22.
They are: Brora Rangers v Brechin City, Clachnacuddin v Keith, Formartine United v Inverurie Loco Works, Forres Mechanics v Nairn County, Fort William FC v Buckie Thistle, Huntly v Fraserburgh, Lossiemouth v Turriff United, Strathspey Thistle FC v Deveronvale, Wick Academy v Rothes.