A decade ago there was a clear gap in our operational environmental prediction capabilities, and associated decision support guidance, at lead times beyond ten days and less than one month. Recognizing the need for making advances in the scientific understanding, model fidelity and prediction capabilities that could fill this gap, US CLIVAR formed the Madden-Julian Oscillation Working Group (MJOWG; 2006-09), as the MJO represented an obvious, unexploited source of predictability at these time scales. The MJOWG focused on advancements on two fronts, experimental to operational prediction of the MJO and weather/climate model experimentation, diagnostics and performance metrics. The former led to a multi-national operational MJO prediction capability hosted at NCEP/NOAA. The successful efforts of the MJOWG, and remaining work to do to further these objectives, led to the subsequent formation of the WCRP–WWRP MJO Task Force (MJOTF; 2010-present). Expanding the MJOWG efforts, the MJOTF advanced experimental to operational predictions of the boreal summer Intraseasonal Oscillation (BSISO). The multi-national operational BSISO predictions have been available since 2013 and are hosted by the APEC Climate Center (APCC), providing guidance on BSISO-driven onsets and breaks of the Asian summer monsoon. The success of these initial R2O MJO/BSISO prediction efforts led, in part, to the formation of the WCRP-WWRP Subseasonal to Seasonal (S2S) Prediction Project and North America Multi-Model Ensemble (NMME) designed to improve the skill of S2S forecasts and advance their utilization by the applications community. The above developments, projects and capabilities, including key multi-model research experimentation, will be discussed, highlighting the role of US CLIVAR, and concluding with a summary of the outcomes and recommendations of the 2015 National Academy of Science report on Developing a U.S. Research Agenda to Advance Subseasonal to Seasonal Forecasting.