Its survey indicates 70% of UK adults, 31 million, watched TV via free catch-up services such as BBC iPlayer and ITV Hub in September and October.
Meanwhile, 16% of web-connected adults viewed catch-up TV on a tablet.
Traditional live TV remained the most popular way of tuning in, however.
Of the 9,000 individuals surveyed, more used these tech-savvy television services in the UK than in the US, France, Germany, Italy, Japan, Australia, Spain or Sweden.
"UK viewers won't be tied to the TV schedule this Christmas," Ofcom director of research James Thickett said.
"More than anywhere else, we're watching TV and films at a time that suits us, on a range of devices, in and out of the home.
"So this year, more people can fit their festive TV viewing around opening presents and carving the turkey."
British viewers are more likely than those in other developed nations to watch on-demand TV this Christmas, the UK's telecoms regulator Ofcom is predicting.