Stock index futures rose on Wednesday, putting Wall Street on track for a third day of gains as optimism grew that Greece's parliament would pass an austerity plan critical to avoiding a debt default.

The vote is expected over the next few hours, and anticipation of parliament's approval has sparked a two-session rally, helping to erase losses partly brought on by the crisis. But gains have come on anemic trading volume, suggesting that caution remained and further upside could be limited.

In a boost to passage of the austerity measures, one of three rebels in Prime Minister George Papandreou's ruling Socialist party changed heart and said he would support the plan, which is vital to getting bailout funds from the European Union and International Monetary Fund. For details, see [nL6E7HT08Q]

Oliver Pursche, president at Gary Goldberg Financial Services in Suffern, New York, said it was unlikely stocks would spike after passage. The market has rallied this week as confidence grew, and I think that most of the benefit has been priced in at this point, he said.

There's also a concern about trading volume being so light on positive days, he added. That confirms we're in a trading range, though not a significant downtrend.

S&P 500 futures added 6.6 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures gained 54 points, and Nasdaq 100 futures rose 11.75 points.

U.S. crude oil advanced again, rising 1.2 percent on optimism over the Greece vote. Energy, a weak sector recently, has helped lead stocks higher this week.

Bank of America Corp settled nearly claims related to Countrywide mortgage-related claims for $8.5 billion in cash. Shares of the Dow component rose 5.3 percent to $11.39 in premarket trading.

May pending home sales are scheduled for release at 10 a.m. <1400 GMT> and are seen rising 3.8 percent after a steep fall in the previous month. Positive housing data on Tuesday lifted optimism over the hobbled sector.

We think sales will come in much higher than expected, and that could be something to move the markets upward today after the Greece vote, Pursche said.

BJ's Wholesale Club Inc rose 4.8 percent to $50.40 premarket after agreeing to be bought by private equity firm Leonard Green & Partners and another group in a deal valued at about $2.8 billion.

General Mills Inc forecast weaker-than-expected full-year earnings due to higher costs. Also, Family Dollar Stores Inc posted lower-than-expected quarterly profit, and the stock fell 1.1 percent in light premarket trading.

Overseas, Japan's industrial production rose faster than expected, suggesting a rebound after the country's recent earthquake and tsunami.

U.S. stocks rose Tuesday, and the S&P is up more than 2 percent so far this week.

(Editing by Jeffrey Benkoe)