In Europe, the FTSE 100 index of leading British shares was up 79.51 points, or 1.6 percent, at 5,218.97 while Germany's DAX rose 82.24 points, or 1.4 percent, to 6,049.73. The CAC-40 in France was 59.54 points, or 1.7 percent, higher at 3,527.56.
Wall Street was poised for a solid opening after a rebound from day lows Tuesday — Dow futures were up 28 points, or 0.3 percent, at 10,206 while the broader Standard and amp; Poor's 500 futures rose 4 points, or 0.4 percent, to 1,084.10.
Apple's results following Wall Street's close Tuesday has helped Wednesday's move higher.
The maker of the iPhone reported a 78 percent increase in net income in the April-June quarter to $3.25 billion and a 61 percent revenue improvement to a record high of $15.7 billion.
Its results helped offset some of the gloom generated by mixed economic figures and other corporate results this week.
The outlook for stocks over the rest of the day could well hinge on what US Federal Reserve chairman Ben Bernanke tells lawmakers in his half-yearly testimony.
"In the absence of major data releases Bernanke's testimony will be the main driver for markets but earnings from Coca-Cola and Morgan Stanley will also be of interest," said Mitul Kotecha, an analyst at Credit Agricole.
In Europe, sentiment toward the auto sector was boosted by better-than-expected results from Italy's Fiat, which controls Chrysler. Fiat reported a return to second-quarter profits on improved sales of agriculture equipment and trucks, and said it may raise its 2010 forecasts. Its shares spiked 6 percent to €9.60 ($12.33) in Milan.
Other carmakers, such as France's Renault and Germany's Daimler rose on the back of Fiat's report, as hopes rose that they too may report stronger than anticipated earnings.
As the week progresses, investors will be increasingly focusing on the results of the stress tests into a large chunk of the EU's banks.
The results of the tests are due after Europe's markets close on Friday and a number of investors remain skeptical about whether they are a credible exercise.
"Too many passes, and the tests will be viewed as a rubber stamp; too many failures could drag the euro back down toward the $1.19 level, as well as undermining any equity gains made this week," said Chris Purdy, a trader at Spreadex.
Some of the unease about the stress tests is evident in the performance of the euro over the last couple of days.
Having set a new four and a half month high of $1.3028 Tuesday, the euro has fallen around 2 cents. By late-morning London time, the euro was down 0.4 percent on the day at $1.2833.
Another currency in focus has been the yen, with many currency strategists predicting that it could soon break above last year's high against the dollar, which would open up the potential for a move up to levels not seen since 1995.
That's a concern because a rising yen could hit Japanese exports to the United States, all other things being equal.
The dollar has been hamstrung over recent weeks by a raft of disappointing data, which have reined in market expectations of any imminent increase in US borrowing costs.
By late-morning London time, the dollar was down another 0.5 percent on the day at 87.04 yen.
The yen's rise has been having a fairly dramatic impact on Japanese stocks. The country's Nikkei 225 stock average gave up early gains to fall 21.63 points, or 0.2 percent, to 9,278.83, meaning that it has lost 5.3 percent in the past four sessions.
Hong Kong's Hang Seng advanced 1.1 percent to 20,487.23, South Korea's Kospi added 0.7 percent to 1,748.78 and Australia's benchmark gained 0.2 percent at 4,412.70.
China's Shanghai Composite Index edged up by 0.3 percent to 2,535.39 after big gains in the previous two sessions amid expectations that Chinese authorities are likely to moderate efforts to cool the world's No. 3 economy.
Oil prices, meanwhile, traded below $78 a barrel after a report showed US crude supplies fell less than expected last week, suggesting demand for fuel is still tepid.
Benchmark crude for September delivery up 47 cents at $78.05 a barrel in electronic trading on the New York Mercantile Exchange.
