Depends on where you are staying.
If you happen to be at the Grand Floridian, you're in luck - its QS is open 24/7.
If not, then no.
Resort food courts/QS generally open at 6-7 am, well after you've boarded the bus bound for MCO.
What you can do the night before is pick up pastries, fruit, cereal, sandwiches, juice, milk, etc from the food court/QS in your resort using those credits and keep it in your room fridge until morning.