This atlas composed by more than 1500 spectra of late-type stars (spectral types from G to M) observed simultaneously in the optical and Calcium Triplet spectral ranges. These spectra were obtained as part of a survey to search for cool supergiants in the Magellanic Clouds and taken over four epochs. We provide the spectral and luminosity classification for each spectrum (71% are supergiants, 13% are giants or luminous giants, 4% are Carbon or S~Stars and the remaining 12% are foreground stars of lesser luminosities).