Catalysis of the reaction: a beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine + UDP-alpha-D-galactose = a beta-D-Gal-(1->4)-beta-D-Glc-(1<->1)-Cer(d18:1(4E)) + H+ + UDP.
UDP-galactose glucosylceramide beta-1,4-galactosyltransferase activity