‘Many players did not do what they were supposed to,’ Van Bronkhorst said after the match. FC Oss is currently 15th in the Jupiler league while Feyenoord heads up the Eredivisie with six wins from six matches.
The score was 1-1 at half time but victory was eventually sealed with goals by Michiel Kramer, Bilal Basaçikoglu and Nicolai Jörgensen.
Elsewhere in the competition, Utrecht put out FC Twente with a score of 3-1 in an Eredivise clash. Utrecht lost in the cup final to Feyenoord last year. Utrecht will meet Groningen in the next round.
Vitesse beat third division side De Dijk 5-1 and will meet RKC Waalwijk in round 2.
In other highlights from the second round draw: PSV takes on Sparta Rotterdam, defending champion Feyenoord meet Excelsior, and Ajax will play amateur side Kozakken Boys in an away match.