A vegetable tray can be made ahead of time for convenience. Ideally, it's best to prepare the vegetables and arrange the platter on the day of serving to ensure optimal freshness. However, if needed, the vegetables can be pre-cut and stored in airtight containers in the refrigerator a day in advance. To maintain crispness, I recommend waiting to assemble the platter closer to the serving time, covering it with a damp paper towel or plastic wrap to keep the vegetables hydrated.