Olivier Ntcham's dramatic 95th-minute goal handed Celtic a 2-1 victory at the Stadio Olimpico on Thursday, their first ever win in Italy, and booked their place in the last 32 of the Europa League with two games to spare.
Rangers are also on the brink of joining their cross-city rivals in the knockout stages as goals from Alfredo Morelos and Steven Davis saw two-time European Cup winners Porto well beaten 2-0 at Ibrox.
The Europa League may not offer the same prize-money windfall or the glamour of the Champions League, but for clubs unable to compete financially with the European elite, it provides the opportunity to compete on a more level playing field.
Celtic have been on the wrong end of thrashings at the hands of Barcelona and Paris Saint-Germain in the Champions League in recent seasons, but have taken 10 points from a possible 12 in Europa League Group E to eliminate French side Rennes and leave Italian Cup holders Lazio's chances of qualification hanging by a thread.
Despite another poor showing from Scottish clubs outside the top two in Europa League qualifying, Celtic and Rangers' exploits mean Scotland has the fifth highest coefficient in Europe so far this season, ahead of France and Italy.
Seven years to the day since a seismic Champions League win over Barcelona, Celtic manager Neil Lennon said beating Lazio, who sit fourth in Serie A, ranked just behind that victory during his first spell in charge.
"I'm so proud of them, not just for winning the game, but the way they played -- the character, the bravery and above all else, real quality," he said.
Not to be outdone by the green and white half of Glasgow, Rangers' revival under former Liverpool captain Steven Gerrard continued with a highly-impressive win over Porto, who reached the quarter-finals of last season's Champions League.
Gerrard's men also drew 1-1 away in northern Portugal two weeks ago, and another point away to Feyenoord in Rotterdam on November 28 will guarantee the presence of two Scottish sides in Europe beyond Christmas for the first time since 2008.
That was the year Rangers reached the final of the UEFA Cup.
"We beat a good team tonight and we've beaten them comfortably," said Gerrard. "Over two games we have dominated three halves."
Rangers are just in their third season back in European competition following a six-year absence after the club was liquidated in 2012 and forced to start over in Scotland's lower leagues.
Celtic took advantage of their demise to rack up eight league titles in a row, but Rangers are also fighting back on the domestic front.
Only one extra Celtic goal separates the two at the top of the Scottish Premiership and Rangers have the chance for their first major trophy in seven years when the two sides meet in next month's League Cup final.
Morelos has been the driving force behind Rangers' fine form as he took his tally for the season to 21 goals in 25 games against Porto, and Gerrard has been keen to stress there is no need to cash in on the Colombian in the January transfer market.
"I will never get bored of talking about him," added Gerrard. "He is a top player and I can't describe how much I enjoy working with him. He's a massive, massive asset to this club."