Compositions and methods are provided for efficiently preparing a completely deglycosylated antibody where efficiency is measured in relative amounts of reagents in soluble or lyophilized form, and time and temperature of the reaction. Compositions and methods are also provided for separating substantially all N-linked glycans from a glycosylated antibody and for preserving functionality of the antibody. The methods are compatible with glycan labeling and protease digestion without the need for prior purification steps.