The department said a fuller set of data showed a higher level of fixed investment by companies and the government, contributing to the 0.2 point upward revision from July's number.
The 4.2% annual pace in the April-June period followed a 2.1% contraction in the first quarter, the consequence mainly of unusually severe winter storms that had battered the eastern half of the United States, depressing economic activity.
In the second quarter, the revised data showed pickups in consumer spending and business investment, and improved government spending and home building.
On the other hand, gross domestic product was dampened by an increase in imports, not surprising given the rebound in activity after the first quarter, analysts say.
The new report left its key inflation indicator unchanged: the price index for gross domestic purchases stayed at 1.9%, up from 1.4% in the first quarter.
The threat, or lack of, inflation has been key to debates over whether the Federal Reserve needs to tighten monetary policy sooner rather than later to prevent price increases from getting out of hand.
The report also showed that corporate profits and spending mostly recovered from the first quarter downturn.
Jay Morelock of FTN Financial called that "a welcome development that will hopefully lead to hiring in the second half of the year."
"Once wages follow the upward trend in business spending, a prosperous cycle could lift the economy toward the 3% trend that remains a fixture of consensus forecasts and stock price assumptions."
The economy's rebound has not been uniform, as Federal Reserve chair Janet Yellen has repeatedly pointed out.
Though job creation has picked up, there remain a huge number of people underemployed or out of the labor market, and wages have remained fairly flat in the recovery from the 2008-2009 recession.
Jim O'Sullivan of High Frequency Economics pointed out that the revised data showed lower nominal growth in wages in the second quarter than previously estimated, 4.7% year-on-year instead of 4.9%.
However, he said, "the data suggest that average hourly earnings are understating the extent to which tightness in the labor market is putting upward pressure on costs and boosting consumer spending power."