Assuming that the fn_GetOrgIdList returns a table then surely You're better doing something.

INSERT INTO @table(ID)

SELECT Table2.ID

FROM Table2 WITH(NOLOCK)

JOIN dbo.fn_GetOrgIdList(@StrId) org on org.<col>=Table2.ParentId

You might get an optimisation from also doing

IF (Select REP from Table1 Where Id=@strId)=1

BEGIN

END

Those are just a couple of ideas, but without knowing what fn_getOrfIdList(@var) does its difficult to advise.