Amid intensifying climate change and escalating environmental degradation, achieving environmental sustainability has become a pressing global challenge, particularly for highly industrialized and energy-intensive economies in the OECD region. Despite growing scholarly attention, prior empirical studies have not sufficiently examined how financial stability, environmental policy stringency, and renewable energy collectively influence environmental sustainability. Addressing this gap, the present study investigates the heterogeneous effects of economic growth, renewable energy consumption, non-renewable energy consumption, hydro energy consumption, foreign direct investment (FDI), environmental policy stringency, and financial stability on environmental sustainability. Using balanced panel data for OECD countries from 2000 to 2020, the study employs the innovative Method of Moments Quantile Regression (MMQR) estimator to capture variation across the conditional distribution of environmental sustainability. The empirical results reveal that renewable energy consumption, hydro energy consumption, stringent environmental policies, and financial stability enhance environmental sustainability across heterogeneous quantiles. Conversely, economic growth, non-renewable energy consumption, and FDI undermine environmental sustainability across heterogeneous quantiles. The study recommends that OECD economies should expand the share of renewable and hydro energy through clean energy investments and subsidies, strengthen the enforcement of environmental regulations, incentivize green FDI through environmental screening and tax benefits, and integrate climate-related risks into financial supervision. Furthermore, implementing carbon pricing mechanisms and allocating the resulting revenues toward renewable energy R&D and green innovation are crucial for achieving long-term sustainable development.