Abstract: Apparatus and method for variable opening of an envelope is disclosed. The apparatus includes a device for supporting the front panel and flap of an envelope in a plane, and a vacuum bar assembly situated above the supporting device, the assembly having a vacuum cup for gripping the back panel of the envelope. The apparatus includes a device for moving the vacuum cup downward to grip the envelope back panel and to move the cup upward a predetermined distance whereby the back panel is separated from the front panel to thereby open the envelope a predetermined amount. The apparatus also includes a measuring system for measuring the thickness of successive collations, and means responsive to the measuring system for controlling the amount of movement of the vacuum cups so that the predetermined amount of movement thereof varies from envelope to envelope to open each successive envelope only the amount required to accept the collation intended for that envelope.