obsolete O-glycan processing, core 4 (obsolete GO:0016270)
OBSOLETE. The stepwise addition of carbohydrate or carbohydrate derivative residues to the initially added O-linked residue (usually GalNAc) to form the core 4 O-glycan structure, GlcNAc-beta-(1->6)[GalNAc-beta-(1->3)]-GalNAc.