We have described an experiment for observing optical feedback ideal for an advanced undergraduate lab. Experiments using tunable diode lasers have become common in undergraduate laboratories, making an investigation of the feedback process extremely valuable. This setup has two main methods for increasing the understanding of laser diodes. First, the diffraction spectrometer setup described here allows the observation of both laser mode spacing and wavelength. When combined with a laser in the Littman - Metcalf arrangement, there is additionally the opportunity for undergraduates to investigate the control of the laser frequency and tunability resulting from optical feedback. The simplicity and low cost of the setup combine to make this an excellent means for introducing undergraduates to optical feedback.