The Iceland international got the decisive double in the final 20 minutes, one from the penalty spot, in a match in which three players were sent off and which sees Heerenveen move up to third in the standings.
AZ Alkmaar advanced to fifth place with a comfortable 3-0 home win over newly promoted Go Ahead Eagles, putting themselves within three points of leaders PEC Zwolle in a congested list of early season frontrunners.
NAC Breda registered their first league success of the season in emphatic fashion with a 5-1 away pasting of Roda JC Kerkrade.
But NEC Nijmegen's hopes of achieving the same breakthrough after five winless matches were snatched away from them in the last minute as Feyenoord equalised in a 3-3 draw.
Dutch international Bruno Martins Indi scored the all-important equaliser but it did not stop Feyenoord coach Ronald Koeman from raging against his own side.
"We have all failed. We twice gave away a lead and surely if you score three away goals you should win the match," he told Dutch radio.
Two goals from Steve de Ridder saw FC Utrecht go some way to putting behind them a poor start to the season as they beat RKC Waalwijk 2-1. The win moved them out of the relegation zone.