Gallacher, who had last found the net in Rome at the tail end of the previous qualifying campaign, ended his famine midway through the first half. If that goal was a trifle scrappy, the Blackburn striker's second, just as Austria were mounting a belated search for an equaliser, was sublime.
Seldom, if ever, can a victory by a team wearing blue have been greeted with such unanimous acclaim at this green citadel. The temptation now will be to assume that Scotland's place in next year's finals is all but assured, but Craig Brown was quick to counsel caution afterwards.
"The section is by no means over," the Scotland manager said. "We hope Austria do well at home to Sweden - which they're capable of doing at full strength - and obviously that we get a result in Gothenburg next month.
"There's a lot of work to do before we can say we're going to France. Any complacency could cost us. But we played the European style tonight which we've been trying to develop. We're getting better at keeping the ball. We played Austria at their own style and came out on top."
Provided there are no further gaffes along the lines of the goalless stalemate with Estonia in Monaco, a draw in Sweden would confirm the Scots as favourites to win their group. Judging by their defensive record - a staggering 14 clean sheets in the last 15 competitive fixtures - few countries are as well equipped to play for a point.
Yet on last night's evidence, perhaps Scotland should be thinking in terms of completing a prestigious double over the Swedes, whom they beat slightly fortuitously at Ibrox in November.
Given Brown's meticulous preparation, nothing is impossible. Here he pulled a tactical masterstroke by omitting Paul McStay in favour of Paul Lambert, who has hitherto been a peripheral figure. The change gave the midfield genuine balance, but more importantly, Lambert negated the threat of Andreas Herzog.
Brown explained: "Paul had done a man-marking job on Herzog - who is Austria's best player - for Dortmund against Bremen when his team won 4-0. I made up my mind a while ago that I'd use him in that role, and it proved to be the key, although I also thought John Collins and Gary McAllister controlled the match.
"Gallacher showed superb movement up front and Darren Jackson also did well. Darren came to me this morning and said he hadn't slept because of bruising from Saturday's Estonia match. He was on the verge of pulling out, but I managed to persuade him."
The burgeoning partnership between these two mobile forwards reaped a handsome dividend after 25 minutes of tentative football. Gallacher's deft first-time touch just inside Austria's half released Jackson to run at Michael Konsel. The goalkeeper parried the shot but appeared to bring down Jackson as he nudged the rebound across goal.
Screams for a penalty turned into an outpouring of joy as Gallacher arrived to bury the loose ball at the ground where he worshipped as a boy.
Austria had a strong penalty appeal rejected themselves early in the second half after Tom Boyd toppled Toni Polster. The referee awarded a free-kick inches outside the box, but if either team was spurred by the incident, it was Scotland.
Indeed, Jim Leighton did not have to make a save worth the name until the 74th minute, when a brilliant diving stop denied the substitute Ivica Vastic.
Three minutes later, however, Gallacher killed the contest. When a pass by Lambert, his principal rival as man of the match, broke off an Austrian defender, Gallacher was lurking near the angle of the 18-yard area.
One touch and a dipping diagonal volley sailed beyond Konsel to complete both the victory and Gallacher's "greatest night in a Scotland shirt". Scottish euphoria was as deafening as it was unrestrained.
SCOTLAND (3-1-4-2): Leighton (Hibernian); Calderwood (Tottenham), Hendry (Blackburn), Boyd (Celtic); Lambert (Borussia Dortmund); Burley (Chelsea), McAllister (Coventry), Collins (Monaco), T McKinlay (Celtic); Gallacher (Blackburn), Jackson (Hibernian). Substitutes: McGinlay (Bolton) for Jackson, 73. McCoist (Rangers) for Gallacher, 86; McStay (Celtic) for McAllister, 88.
AUSTRIA (1-2-5-1-1): Konsel (Rapid Vienna); Feiersinger (Borussia Dortmund); Schottel (Rapid Vienna), Pfeffer (Austria Memphis); Schopp (Hamburg), Heraf, Stoger (both Rapid Vienna), Aigner (Casino Salzburg), Wetl (Porto); Herzog (Werder Bremen); Polster (Cologne). Substitutes: Kogler (Casino, Salzburg) for Schottel h-t; Vastic (Sturm Graz) for Stoger, 67; Ogris (Austria Vienna) for Aigner, 81.
Referee: N Levnikov (Russia).
World Cup reports,
Last night's results, page 29
World Cup Group Four
P W D L F A Pts
Scotland 6 4 2 0 7 0 14
Austria 4 2 1 1 3 2 7
Sweden 4 2 0 2 7 4 6
Estonia 4 1 1 2 1 3 4
Belarus 4 1 1 2 3 7 4
Latvia 4 0 1 3 3 7 1
REMAINING FIXTURES: 30 Apr: Austria v Estonia; Sweden v Scotland; Latvia v Belarus. 18 May: Estonia v Latvia. 8 June: Estonia v Sweden; Latvia v Austria; Belarus v Scotland. 20 Aug: Estonia v Austria; Belarus v Sweden. 6 Sept: Austria v Sweden; Scotland v Belarus; Latvia v Estonia. 10 Sept: Sweden v Latvia; Belarus v Austria. 11 Oct: Austria v Belarus; Scotland v Latvia; Sweden v Estonia.Reuse content