Method and plant for manufacturing parisons of oriented thermoplastic resin, particularly adapted to be subsequently blow moulded for forming into bottles, comprising the phases of injection of the molten resin into a plurality of multicavity moulds, solidification of the respective parisons until a definite temperature is reached, removal of the parisons from the injection moulds and transfer thereof into appropriate rapid-cooling cups, said cooling action occurring by closing the mouth (6) of the parison (2) after the introduction thereof in the respective cup (1), and letting gas under pressure into the cavity of the parisons so as to enable the outer surface thereof to enter into contact with and to conform to the inner surface (3) of the respective cup (1) for a predetermined time. In a preferred manner, said cups (1) are cooled through the provisions of channels (10) in which a cooling medium is circulated. Advantages: the dwelling time of the parisons in the respective injection mould is reduced, while the cycle time rate and, as a result, the productivity of the method/plant is increased.