You can create an instance of FlatDataSource object and set its ItemSource property to your ObservableCollection such as:

FlatDataSource flatData = new FlatDataSource();

flatData.ItemsSource = new Cars().GetCars();

this.DataContext = flatData;

I am attaching a sample that demonstrates it.

Sam 

Thanks for the article.  I will be more specific with my question:

How do I use an observable collection (property) on my viewmodel as a source of data for a xampivot grid?  Note this is not a static resource.

Thanks,

Sam