Defining the form factor and setup of surfaces, i.e., their size, position , and orientation, is one of the first decisions made when designing multi-surface environments (MSE). To support these choices, we conducted a study on how the orientation of a large display used alongside tablets impacts collaboration. Previous research involving only one interactive surface shows that display orientation changes how people interact with the display, the way they position themselves, or look at each other. Our study shows that in a MSE setting, the orientation of a large surface has a different impact: (1) it nuances previous results showing that horizontal surfaces are better for collaboration. (2) it impacts the way activities are conducted. The horizontal condition leads to more implicit coordination and balanced interaction with the large display, but to less structured work, while in the vertical condition, group coordination is more explicit and is structured around one main interactor. Compared to previous work, we also propose a more structured, comprehensive and detailed analysis grid for collaboration in MSE. Finally, based on our results, we derive recommendations for MSE design.