Ok, that's my first 'Duh' moment of the day... I used a combination of the 'Optimize For' and 'Recompile' hints and got the execution time back down to <...

Not sure it will help, but here's the full query...

ALTER PROC NA001MissingTimeReport @DateStart Date, @DateEnd Date, @PeriodID nvarchar(10), @Agency nvarchar(5), @Department nvarchar(20), @Worker bigint = 0,

@AccrualFormat bit, @IncludeFreelancers bit,...

Here are the parameters that I'm passing, and I'm using the two Date parameters in multiple places inside the dynamic SQL statement.

SET @ParmDefinition = N'@DateStart Date,' + @NewLine

+ '@DateEnd...