Bruce struck after only 12 minutes of the derby, firing a wonderful half-volley into the net from the edge of the box.
It was enough to deliver the win, Nobby Stiles’ men holding on to the lead quite comfortably.
Victory saw North End do the double over Rovers, having beaten them 4-1 at Deepdale in the second league game of the season.
Bruce’s winner was one which PNE fans of the era were able to store in the memory bank for some time.
Granada TV had their cameras at Ewood to cover the game for Sunday afternoon highlights’ show ‘Kick-Off.’
So impressed were the Granana producers with Bruce’s goal, they featured it on the opening sequences well into the next season.
It was a cracker of a goal from the Scottish striker, his 23rd that season – he went on to score 26.
A game played on a bobbly pitch and in a strong wind didn’t allow for much quality football to be played.
But the goal and build-up made light of the conditions.
A headed clearance from the Rovers defence was picked up by Eric Potts who played the ball out to Brian Taylor on PNE’s right.
Taylor’s ball up the wing found Graham Bell who was making his debut after a move from Oldham.
Bell’s cross came to Bruce on the edge of the ‘D’, the striker catching it superbly on the volley.
It stayed low and flew into the far bottom corner past the Rovers keeper.
North End had gone into the game on the back of six successive draws, that far from a poor run in the days of only two points for a win.
Those draws came after a harsh winter which had seen few league games played.
At the other end, Danny Cameron cleared off the line from a Noel Brotherston shot, the shooting chance having been created by the North End left-back Cameron getting into a tangle with keeper Roy Tunks.
In the second half , Rovers came out pushing for an equaliser but found PNE’s defence a solid unit.
When the visitors did get on the attack, they found the going tough without injured striker Mick Robinson.
His place for this game had gone to recent arrival Steve Elliott – signed from Nottingham Forest.
Elliott himself was not fully fit, North End manager Nobby Stiles naming striker Ian Cochrane on the bench just in case.
Rovers skipper Parkes misjudged a header at the far post from Duncan McKenzie’s cross, allowing Don O’Riordan to clear.
Chances came North End’s way with Bruce heading a Taylor cross wide and Mick Baxter off target after getting on the end of a Bell free-kick.
In the closing stages, the home side upped the pressure as they went in search of an equaliser. Commenting on Bruce’s winner, Stiles said: “Alex’s goal was a real cracker, it showed just how good he is.”
The 17,790 crowd was Blackburn’s best that season.
They were to be relegated at the end of the campaign, finishing five points adrift of safety at the foot of the table.
North End finished seventh, a decent show indeed for a side in their first season back at this level.
Interviewed by the Evening Post in 2015, Bruce fondly recalled the goal.
Bruce said: “I scored at the other end of the ground to where the North End supporters were.
“Graham Bell put a ball in and I just sensed their centre-halves were going to miss it.
“I don’t know if I was a bit lucky but I hit the ball really well and it flew into the net.
“The footballs were a lot heavier back then, compared to what they use now.
“To hit a shot as hard as I did, you had to catch it well.
“I shocked myself because I rarely scored from outside the box!”