A composite magazine for feeding to a filling or packaging machine pre-formed and flattened containers includes a main magazine suitably inclined in which the containers are piled up. The main magazine includes a long upper back portion which can be opened and closed downwardly. Below the main magazine there is provided an ancillary magazine which initially is in a substantially horizontal loading position in order to be easily supplied with a pile of containers on a bottom plane which leaves uncovered lateral portions of the bottom of the pile. When the upper back portion is emptied, the upper back portion is opened and the ancillary magazine is raised to insert the pile of containers in the main magazine. The upper back portion then closes to retain the pile, while the ancillary magazine returns in the low loading.