Home Postcodes by state QLD 4378 Postcode 4378 4378 is the postcode for Applethorpe, QLD. Localities with postcode 4378ApplethorpeQLD Postcode 4378 State or territory Queensland (QLD) Localities 1 Council area Southern Downs Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 4377 · Postcode 4380