You can also try getting the default value directly from the result of a dataset query. This is a fully dynamic way to get what you want :

SELECTDATEADD(d, -1,

DATEADD(q,DATEPART(q,getdate())-1,CAST(year(getdate()) AS varchar(10)))

) AS myDefaultDate

Of course you next set the default value of the report parameter to source from a query, using this dataset.