There was a first goal for more than three years for Steven Reid, a first in English football for Michel Salgado and a first, more importantly, for £6million striker Nikola Kalinic.
Progress to the Carling Cup quarter-finals for the third successive year was achieved as Sam Allardyce's men sandwiched the daunting trips to Stamford Bridge and Old Trafford with a five-goal display.
No way back: Michel Salgado celebrates scoring the crucial third goal for Blackburn
Sir Alex Ferguson's side await them on Saturday. Son Darren'sPeterborough were seen off, though not without a fight. They equalisedtwice, the second time with only 10 men after keeper Joe Lewis was sentoff.
Not that the evening began well for the England Under 21international. His first task was to remove the ball from the back ofthe net after Morten Gamst Pedersen's perfectly placed free-kick.
Posh responded. Chris Whelpdale headed in Tommy Rowe's deep cross.
After Kalinic hit the bar, Pedersen made his mark again and Lewis left the pitch. Russell Martin's header back to his keeper was woefully misjudged, allowing Pedersen to nip in.
Lewis brought him down and got his marching orders. Reid scored the resulting spot kick.
Green army: Peterborough celebrate their first equaliser, scored by Chris Whelpdale
To Rovers' fury, Republic of Ireland manager Giovanni Trapattoni hadquestioned the midfielder's ability to play top-level football again.
As he found the net for the first time since 2006, this was an eloquent reply.
Peterborough provided a reaction of their own. George Boyd, who wasoutstanding, scored his ninth goal of the season, with an unstoppablestrike.
But then came the decisive goal. Salgado is more accustomed towinning the Champions League than the Carling Cup, but he effectivelyensured Rovers' progress.
The right back recruited from Real Madrid finished well from six yards.
Spot on: Nikola Kalinic rounds off the scoring with his team's second penalty of the night
Victory was completed by the combination of Allardyce's two strikers.
Benni McCarthy doubled his tally for the season with a side-footed shot after Kalinic led a break away.
Then came the Croat's moment. After Krystian Pearce handled, he wasgiven the penalty and Allardyce's biggest summer signing duly openedhis account.
Neil McDonald, Blackburn's assistant manager, said: 'A performance like that gives everybody confidence.'
BLACKBURN (4-4-2): Brown; Salgado, Jones, Givet, Olsson; Hoilett, Emerton, Reid, Pedersen; McCarthy, Kalinic. PETERBOROUGH (4-4-1-1): Lewis; Lee (Martin 35), Pearce, Morgan, Rowe; Whelpdale, Frecklington, Diagouraga, Boyd; Mclean, Batt (McKeown 43).
Sent off: Lewis.
Man of the match: Morten Gamst Pedersen.
Referee: Anthony Taylor.
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