The men's 200m semi-final, which saw Usain Bolt stroll to a place in the final, attracted its highest audience at around 8.15pm.
More athletics dominated BBC One's schedule in the morning, logging 2.45m (36.3%) between 9am and 11.30am, and 3.04m (40.2%) from 11.30am until 1pm.
Interest then dipped to 2.37m (29.9%) from 1.45pm for a mixture of women's boxing and show jumping.
Olympics Breakfast (1.69m/42.8%) had over three times Daybreak's audience in the breakfast TV slot.
BBC Three peaked with 849k (9.1%) at 4.15pm for its programme which included hockey, table tennis and men's basketball.
BARB ratings data supplied by Attentional
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