OSIRIS (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy) Multi-Object Spectroscopy (MOS) observing mode is available to the science community of the GTC (Gran Telescopio Canarias) from early 2014. The MOS production line allows the researchers to specify a MOS observation in a self-contained way by using a software tool, in order to bridge the gap between science aims and the multiplexed spectroscopic data gathering at the telescope. It gives the researcher the guarantee that the observation will perform as expected, thanks to the computer vision based quality control checks of the masks produced. This article describes the architecture of the production line of MOS observations, its activities, actors, and subsystems, and how all of them mesh so that the production line works efficiently and effectively, in an automatized way, using a model-centric approach where the observation design acts as the single source of truth for the entire organization.