The present disclosure provides methods for analyzing structure and/or composition of glycoproteins and glycans of glycoproteins. Such methods can include subjecting a glycoprotein preparation to a condition that removes at least one O-linked glycan from the glycoprotein. Such methods can include subjecting a glycoprotein preparation to a condition that releases an N-glycan from the glycoprotein, e.g., prior to subjecting the glycoprotein to a condition that releases an O-glycan from the glycoprotein.