American Thanksgiving in Durham Region
In Oshawa there is Teddy's which does a gorgeous turkey dinner with trimmings. Very delicious and an insane portion! Expect leftovers. This is offered every day of the year actually. And very reasonable at just over $12.
However - they only make pumpkin pie (which is divine) for Canadian Thanksgiving. At least that is how I understand it. You can always call and request it though. Who knows, maybe they'll oblige (they are very customer-oriented). If not, they house-make a strawberry pie and coconut cream pie daily.