Responsible innovation requires, among other things, that innovators reflect on the broader socio-ethical and socio-economic context of their work. This may be done by reflecting on innovation project complexity. However, tools and methods enabling relevant reflection are not abundant. In this explorative study, we investigated the effect of explicitly stimulating reflection about complexity during innovation project front-end development, using Midstream Modulation (MM) in combination with a complexity framework that distinguishes technical, organizational and external (TOE) aspects. Three project leaders in engineering and construction within the Dutch process industry interacted regularly with a critical outsider, following MM protocols, while also discussing relevant TOE aspects. Our method proves useful in supporting deliberations, and helps to broaden and deepen considerations regarding TOE aspects. The findings show the possibility and utility of enhancing reflection during early phases of innovation project management, in a way that advances both ongoing projects and responsible innovation objectives.