N-acetyl glucosamine (GlcNAc) transferase that catalyzes the transfer of GlcNAc via a beta1->3 linkage from UDP-GlcNAc to the non- reducing terminal galactose (Gal) in the linearly growing chain of N- and O-linked keratan sulfate proteoglycans. Cooperates with B4GALT4 galactosyltransferase and CHST6 and CHST1 sulfotransferases to construct and elongate mono- and disulfated disaccharide units [->3Galbeta1->4(6-sulfoGlcNAcbeta)1->] and [->3(6-sulfoGalbeta)1->4(6- sulfoGlcNAcbeta)1->] within keratan sulfate polymer (PubMed:14706853, PubMed:17690104). Involved in biosynthesis of N-linked keratan sulfate proteoglycans in cornea, with an impact on proteoglycan fibril organization and corneal transparency (By similarity) (PubMed:17690104). May play a role in the maintenance of tissue architecture by suppressing cellular motility and invasion (By similarity). {ECO:0000250|UniProtKB:Q8K0J2, ECO:0000269|PubMed:14706853, ECO:0000269|PubMed:17690104}. This is the function of B3GNT7 (UDP-GlcNAc:betaGal beta-1,3-N-acetylglucosaminyltransferase 7, Ensembl gene identifier ENSG00000156966).