In the 2015-2016 season, De Groot took part in various DNO talent activities and was assistant conductor for Il matrimonio segreto (Cimarosa). He has worked with Opera Zuid as rehearsal director (La bohème) and assistant conductor (Il barbiere di Siviglia, Un ballo in maschera and A Quiet Place). Since the 2016-2017 season, he has been working with the Dutch National Opera Chorus as assistant chorus master. In the summer of 2018, De Groot was assistant chorus master at the Bayreuther Festspiele. Later that season, he was also chorus master and assistant conductor for Fantasio with Opera Zuid, of which he conducted three performances.
DNO productions: Die Entführung aus dem Serail, La bohème, Juditha Triumphans