The aim of this study was to test the ability of visible-near infrared (Vis-NIR) reflectance spectroscopy to predict beef quality traits in the slaughterhouse by directly applying a fiber-optic probe on the carcass surface. Carcasses from 230 young bulls and heifers slaughtered in two commercial abattoirs were included in the experiment. Vis-NIR spectra were recorded on an exposed surface of M. gracilis in the abattoirs 4 to 6 and 14 to 16 h post mortem. Traits evaluated were pH, color indexes (L*, a*, b*, H, and SI), cooking loss, and Warner–Bratzler shear force. Prediction models were satisfactory for pH and color indexes, and promising for cooking loss but not for Warner–Bratzler shear force. Results of this work show that Vis-NIR spectroscopy may be a useful tool for on-line prediction of some physical beef quality traits when applied directly on the carcass surface.