The invention relates to a method for operating an order-picking systems (100; 100′), wherein the order-picking system comprises a high-bay warehouse (10), at least one tray warehouse (16), at least one packing station (20; 32), and at least one shipping station (22), comprising the following steps: a) depalletizing (S20) in a layerwise manner packing units (42), which form a, particularly complete, pallet layer (40), from a pallet (44), particularly a EuroPallet, which respectively carries a plurality of packing units (42), which are to be picked, of a type of article, onto a correspondingly dimensioned tray (46); b) bringing (S30) the tray (46) loaded with the pallet layer (40) into the tray warehouse (16), preferably by means of a conveyor technique (14), a storage machine and/or a lift; c) recalling (S40) the tray (46) loaded with the pallet layer (40) in accordance with an order-picking order or several order-picking orders to the packing station (20; 32); removing in accordance with the order-picking order or one of the order-picking orders a predetermined number of packing units (42), which are to be picked, and packing the retrieved packing units onto a shipping support, in order to ship the shipping support to the customer, if the order-picking order is completed.