The BBC1 show, which features former primary school headteacher Val Stones, 66, among its contestants, attracted an average of 10.4 million viewers as it returned for a seventh series.
The episode was watched by 47.5% of all television viewers with a peak audience of 11.2 million at 20:50.
That means it beat the most-watched moments of the Rio Olympics, which peaked at 11.1 million viewers.
Jane Beedle was named the first star baker of the series while church minister Lee Banfield - the oldest contestant at 67 - was the first to leave after judge Paul Hollywood said one of his cakes was too dry.
Val, who now lives in Yeovil, survived the first week - despite a series of mishaps and baking blunders during the show.
Some 13.4 million people tuned in to see Nadiya Hussain win the last series, making it the most-watched programme of 2015.
Last year's opening episode was watched by 9.3 million viewers, according to overnight figures, peaking at 10 million.