Late Groningen strike denies Ajax winning start
New signing Mounir El Hamdaoui opened the scoring five minutes into the second half and added his second 11 minutes later when he picked up a pass from Demy de Zeeuw before turning and firing into the net.
Tim Matavz pulled one back for Groningen before Pedersen salvaged a point for the home side.
Feyenoord scored three second-half goals to overcome Utrecht's 12th minute opening goal when Ricky van Wolfswinkel netted a rebound.
An own goal by Alje Schut after the break put Feyenoord back on track, while a long drive from Luigi Bruins and a fine header by Leroy Fer sealed the victory.
On Saturday Swede Ola Toivonen struck twice to earn PSV Eindhoven a 3-1 win at Heerenveen, while champions Twente Enschede were held to a goalless draw by Roda JC Kerkrade on Friday.