Some 12m were tuned in to BBC One and Olympics 1 just before 9pm as Greene just missed out on a bronze medal.
Athletics didn't drop below 10 million for much of the evening, helping BBC One to another huge primetime victory.
Beth Tweddle's gymnastics bronze attracted a high of 5.3m at around 3.15pm.
Meanwhile, interest in cyclists Victoria Pendleton and Sir Chris Hoy's fortunes at the Velodrome hit a peak of 7.3m just before 6pm.
BBC Three had a quieter day with a high of over 1.6m at 4.30pm, but still managed to beat Channel 4 and Channel 5 in the all-day shares.
BBC One's Olympics Breakfast managed a hefty 1.65m (41%) between 6am and 9am, while the late-night Olympics Roundup took 2.58m (22.1%) from 10.35pm.
BARB ratings data supplied by Attentional