Two surface-sensitive label-free optical methods, grating coupled interferometry (GCI) and spectroscopic ellipsometry (SE) were integrated into a single instrument. The new tool combines the high sensitivity of GCI with the spectroscopic capabilities of SE. This approach allows quantification with complex optical models supported by SE and accurate measurements with the evanescent field of GCI. A flow cell was developed to perform combined and simultaneous investigations on the same sensor area in liquid (or gas) environments. The capabilities of the instrument were demonstrated in simple refractometry and protein adsorption experiments.