[1] Van Oostenbruggen joined NSC when it was founded by Pieter Omtzigt in the run-up to the November 2023 general election.

[6][7] Van Oostenbruggen said he wanted to improve the Dutch business climate, and he argued that entrepreneurs were underrepresented in parliament.

[2][8] His portfolio includes taxation, customs, financial relations with lower governments, state ownership of Holland Casino and Nederlandse Loterij [nl], and Domains Movable Property.

[9] He complied with requests from the House of Representatives to enforce a ban on false self-employment leniently, by refraining from imposing fines in 2025.

[10] He was tasked with reforming the wealth tax after the Supreme Court had invalidated its reliance on assumed yields in 2021 and had subsequently rejected a proposed transition arrangement.

A bill by one of Van Oostenbruggen's predecessors to tax actual yields was deemed overly complex and difficult to implement by the Council of State in November 2024.