We propose an improved online scheduler for multichannel or Wavelength Division Multiplexed (WDM) Ethernet Passive Optical Network (EPON) upstream transmission. This scheduler employs a just-in-time online scheduling framework to increase the number of Optical Network Units (ONUs) that can be scheduled concurrently. We outline the overall structure of this scheduling framework and discuss adapting offline scheduling policies for use in this framework. We compare the average queueing delay performance of different schedulers that follow this new framework to a simple online scheduler that schedules ONUs as soon as their REPORTS are received at the Optical Line Terminal (OLT). Further, we show how this framework can be used to provide differentiated service to ONUs without waiting for all ONUs to REPORT. We conclude with some remarks regarding our performance findings and possibilities for future research.