Abstract: A serving window for installation in drive-through facilities such as fast food restaurants is disclosed. The window unit comprises two window members carried by rotatable shafts and set in a support frame, preferably of stainless steel, with an operating mechanism mounted within the sill of the support frame and operable electrically or manually by applying pressure to a bump bar mounted on the inside of the window frame or to a foot pedal linked to the operating mechanism by a hidden cable. The operating mechanism consists of a pivotal crossbar mounted horizontally on the support frame and secured on each end to an "L" shaped crank arm arrangement connected to a corresponding window shaft. When the mechanism is activated, the crossbar oscillates within the limited confines of the window frame and effects full opening of the windows in synchronism upon slight pressure applied to the bump bar or one of the other means of operation. Release of pressure on the bump bar automatically closes the windows.