PSV Eindhoven, 6-1 winners over NAC Breda on Saturday, are top with 40 points after 18 matches, ahead of Twente Enschede, who beat AZ Alkmaar 3-0, on goal difference.
Ajax Amsterdam are third with 37 points after being held to a 0-0 draw by Utrecht and with a better goal difference then Feyenoord. The arch-rivals will meet in Amsterdam after the winter break, on January 20.
Feyenoord and Groningen endured a lacklustre first half but 13 minutes after the break Pelle notched up the opener from a corner kick by Jordy Clasie.
Groningen defender Virgil van Dijk levelled the score 13 minutes before time when he picked up a deflected cross and scored but, with three minutes remaining, Pelle struck a tight-angled shot to settle the match.
"(It was) a difficult first half in which we created nothing but we turned the tide after the break because we have a striker who is decisive," coach Ronald Koeman said.
"Last year we had John Guidetti who did perfectly and added some character to the team but Pelle is not only scoring but also always very valuable as target man," he said of the Italian who was signed on loan from Parma on the final day of the August transfer window.
Ajax, who had won their previous six matches, overwhelmed Utrecht in the first half and created several chances but Siem de Jong, Derk Boerrigter and Viktor Fischer wasted them.
Utrecht, who have now gone six league matches unbeaten against Ajax, finished with 10 men after a late second booking for Dave Bulthuis.
Willem II Tilburg finished the first half of the season bottom of the league with 12 points despite a 0-0 draw at neighbours RKC Waalwijk on Sunday.