Inconsistent BAQ performance issues

I have a BAQ that links 11 tables with RcvDtl the primary table.
The only criteria are Company and RcvDtl.ReceiptDate.

If I run the BAQ for all of September, I get 14,089 rows in just under 6 minutes.
If I run the BAQ for all of August, I get 15,013 rows in 5 SECONDS.

If I copy and paste the SQL statement from the BAQ General tab into SQL Server Management Studio, both date ranges execute in under 2 seconds.

Where should I begin to figure out why the date range used in the BAQ makes sure a difference?