The copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction is a powerful tool for bioconjugation of biomolecules, particularly proteins and peptides. The major drawback limiting the use of the CuAAC reaction in biological systems is the copper-mediated formation of reactive oxygen species (ROS), leading to the oxidative degradation of proteins or peptides. From the studies on a limited number of proteins and peptides, it is known that, in general, the copper mediated oxidative damage is associated with the copper coordination environment and solvent accessibility. However, there is a lack of data to help estimate the extent of copper-mediated oxidation on a wide range of proteins and peptides. To begin to address this need, we quantitatively measured the degree of copper-mediated oxidation on libraries of 1200 tetrapeptides and a model protein (bovine serum albumin, BSA) using liquid chromatography mass spectrometry (LC-MS). The collected data will be useful to researchers planning to use the CuAAC reaction for bioconjugaton on peptides or proteins.