Celtic's decision to request a postponement for this weekend's scheduled fixture versus St Johnstone gave Derek McInnes' team a chance to steal a march on the champions.
St Mirren made it tough going for them during the opening exchanges before home goalkeeper Mark Ridgers misjudged a Niall McGinn cross that found a way home to give Aberdeen a fortuitous 31st-minute advantage.
Shay Logan doubled the lead two minutes later, securing a 2-0 win and a four-point lead over Celtic, who now have two games in hand.
Inverness Caledonian Thistle are a point further back in third after Billy McKay's double secured a 2-1 comeback win at Kilmarnock.
John Hughes' team were forced to record a third consecutive victory the hard way after David Raven was sent off for a foul on Josh Magennis that gave Kilmarnock a 47th-minute penalty.
Alexei Eremenko duly converted but McKay fired Inverness level six minutes later and decisively struck again with nine minutes to play.
Dundee ended a run of six games without a win by beating struggling Motherwell 4-1.
Alex Harris and Greg Stewart had the hosts two goals to the good after eight minutes and, although John Sutton prodded home a reply, Gary Irvine restored his team's cushion before half-time.
Motherwell had Henrik Ojamaa sent off after appearing to elbow Kevin Thompson and Mark O'Brien's 70th-minute own goal completed their misery.
The match between 11th-placed Ross County and Partick Thistle in ninth was postponed as a result of a power failure at the Global Energy Stadium.
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