We study the response of a film of colloidal spherocylinders to compression by combining pressure-area isotherm measurements, microscopy, and computer simulations. We find that the behavior of the film depends strongly on the geometry of the particles. For a small aspect ratio, a uniform monolayer forms and then buckles. For a higher aspect ratio, particles flip to orient perpendicular to the interface; we show that flipping occurs in locations where the nematic ordering is low. Our experiments and simulations further demonstrate that the longest particles rearrange to self-assemble a colloidal bilayer, which is stable due to the unique geometry of spherocylinders at an interface.