okay, thanks, I'll check with our provincial forestry ministry for guidance on how to ensure that the seedling survives the winter.
How do they survive in nature?
Trees do not belong indoors. Your oak must go through its cycle, loose its leaves, develop buds and grow new leaves next spring.
If you bring it indoors, it will not go through this cycle. It may grow for a while, but eventually, it will die.
I should have asked... I am not sure what kind of oak you have (I don't know what a 'Great Oak' is). Look up your species, check it's temperature tolerance.