With sides ranked from fifth to eighth in the Eredivisie featuring in a play-off for the league's final European berth, Groningen will have been delighted to see their outstanding form continue.
Erwin van de Looi's side produced a 1-0 home win over Vitesse in Wednesday's first leg, giving them their seventh successive victory.
And their run of wins continued with a 4-1 road success on Saturday that was helped by a late flurry of goals.
Tjarron Chery gave Groningen a 2-0 aggregate lead with the game's opener in the 25th minute but Davy Propper's goal just after the hour-mark gave Vitesse a lifeline.
Groningen responded within a minute through Richairo Zivkovic though, and as Vitesse desperately threw men forward, they were caught out at the back.
Serbia forward Filip Kostic helped himself to a late double as a result, as Groningen sealed a 5-1 aggregate triumph.
The loss has ended Vitesse's season, a campaign that finished with a winless run of nine matches.
Saturday's other semi-final second leg saw AZ progress despite a 1-0 defeat at Heerenveen.
A 3-0 triumph in the first leg gave AZ valuable breathing space and although Luciano Slagveer's 47th-minute effort gave Heerenveen hope, it proved to be a mere consolation for Marco van Basten's men.
Groningen and AZ will now play later this month for a berth in Europe's second-tier competition.
