Five wickets in a stumps total of 262 amounted to far better than what England mustered at The Oval. However, after winning the toss, and under cloud cover either side of teatime rain, Petersen (124no), who followed a fluent first 50 with a stoic second, prevented the hosts from making more telling gains.
England endured an ominously and controversially wicketless first session, then struck three times in the afternoon - once with a run-out - but could not consolidate as the clouds dispersed again.
When Tim Bresnan had Graeme Smith (52) caught at square-leg in early afternoon, he was delivering England's first wicket since he himself last got rid of the opposition captain 10 hours previously - in playing time - dating back to day three in London.
Both James Anderson, after Alastair Cook's dropped slip catch, and then - in bizarre circumstances - Steven Finn came frustratingly close to removing a South Africa opener before lunch.
Cook put Petersen down on 29; then first-change Finn thought he had Smith neatly caught at first slip by Andrew Strauss for six, only for umpire Steve Davis to call dead-ball after the fast bowler repeated his uncanny habit of disturbing the bails at the non-striker's end in his delivery stride.
Petersen was past his 50 before lunch, with a pull at Bresnan for his seventh four, and Smith reached his from 91 deliveries in early afternoon. But he was to succumb at last to England's packed leg-side field, and only three overs later the hosts picked up the big bonus of Hashim Amla's wicket with a run out.
When Cook redeemed himself with a smart catch low to his left, at second slip again, after Jacques Kallis toe-ended an attempted cut at Anderson, South Africa had faltered from 120 for none to 157 for three.
Rain brought an early tea, though, and when play resumed an hour and a half later Petersen was still not for shifting - and AB de Villiers was watchful too in an important stand of 97. Petersen dug out his fourth Test century, with a four off Stuart Broad, before having an lbw decision off Finn overturned on DRS when on 119.
Even De Villiers' chop-on to Broad with the second new ball, and nightwatchman Dale Steyn's clean-bowled duck to Finn, therefore could not alter the complexion of another day when world cricket's balance of power tilted towards South Africa.