Groningen have signed De Graafschap's Berry Powel and FC Zwolle's Anco Jansen.
Powel is seen as an ideal replacement for Erik Nevland, who joined Fulham last week, and has signed a one-and-a-half-year contract at Euroborg.
Manager Ron Jans has also landed Jansen, 18, as the midfielder's contract was set to expire in summer.
Meanwhile, Danny Holla has returned from his loan at Zwolle, and Sander Rozema has been loaned out to Jan Everse's side.
De Graafschap have also loaned defender Jordy Buijis for the rest of the season from Feyenoord.