Execute SQL task returning output variables

I am trying to use the Execute Sql Task to retrieve specific date values from the database that are assigned to package variables. Here is what I have set in the General Setting tab:

The SQL statement is

Select 
Left(Convert(Varchar,(DateAdd(mm,-1,GetDate())),112),6) + '16' as ?,
Left(Convert(Varchar,GetDate(),112),6) + '15' as ?

The User::BegDate and Use::EndDate are defined as strings. Here is the parameters tab:

I receive the error "Incorrect syntax near '@P1'.". Possible failure reasons: Problems with the query, "ResultSet" property not set correctly, parameters not set correctly, or connection not established correctly."

When I execute the statement like this in SQL Query window it returns the values I expect

Select 
Left(Convert(Varchar,(DateAdd(mm,-1,GetDate())),112),6) + '16' as BegDate,
Left(Convert(Varchar,GetDate(),112),6) + '15' as EndDate

I find lots of help regarding input variables, but not output variables. Can you help?

Thanks! paws27284