Abstract: Research institutes frequently collaborate with for-profit publishers for the publication of open access journals. This study uses a structural break test to examine the effects of the collaboration between research institutes and large and small for-profit publishers for the publication of 15 gold open access journals on the journals’ internationality and academic influence. The results reveal an improvement in the internationality and academic influence for most of the journals following the collaboration. Additionally, the scale and persistence of the effects are not dependent on the size of the publisher. The findings indicate that large publishers do not have any advantage over small publishers in publishing journals for research institutes. This implies that small publishers can compete with large ones in publishing official journals on behalf of research institutes. However, as collaboration with research institutes strengthens the large publishers’ presence in the open access journal market, it is necessary to monitor their activities, including large publishers’ acquisitions of small ones.