A Thriller Thursday, which saw a number of British athletes including Jonnie Peacock win gold medals, averaged 3.4m (16.3%) between 7.30pm and 11pm.
More 4's half-hour broadcast of the Games fetched 733k (3.9%) at 7pm.
The Bletchley Circle - ITV's new war drama - premiered with 3.98m (17.7%) at 9pm and 442k (2.4%) on ITV1 +1, while BBC One's Good Cop fell to 3.35m (14.1%).
The Hotel Inspector interested 1.39m (6%) on Channel 5, then Celebrity Big Brother grabbed 1.63m (9.2%) at 10pm.
Wartime Farm appealed to 2.46m (11%) on BBC Two in the 8pm hour, after which 629k (2.7%) tuned in for Hilary Devey's Women at the Top.
Overall in a close race, BBC One edged primetime with 18.7%, ahead of ITV1's 16.9% (+1: 0.7%) and Channel 4's 15.2% (+1: 0.5%). BBC Two finished fourth with 6.2%, followed by Channel 5's 5% (+1: 0.2%).
Celebrity Juice soared to 1.21m (6.5%) on ITV2 at 10pm, adding 205k (2.1%) an hour later on timeshift.
> Today's soap ratings
BARB ratings data supplied by Attentional