* Office Depot posts wider loss, stock sinks
* Consumer confidence data for July on tap (Updates with housing data, quote)
By Ellis Mnyandu
NEW YORK, July 28 (Reuters) - U.S. stocks were set to dip at Tuesday's opening after a handful of companies, including Viacom Inc and Office Depot Inc, posted disappointing quarterly results and investors sought more evidence of the economic rebound.
U.S. single-family home prices rose in May from April, the first monthly increase in nearly three years, suggesting prices may be stabilizing, according to Standard & Poor's/Case Shiller home price indexes on Tuesday.
"It may be the case while this is encouraging, the market is looking for some additional, confirming evidence," said Peter Jankovskis, co-chief investment officer at OakBrook Investments LLC in Lisle, Illinois.
Viacom , owner of MTV Networks and Paramount film studios, reported a steep fall in quarterly earnings, hit by poor advertising revenue and a drop-off in sales of its "Rock Band" video game.
Office Depot, the No. 2 U.S. office supply retailer, reported a bigger-than-expected quarterly loss as the recession hurt demand from corporate customers. Office Depot shares fell 16.8 percent to $4.45 before the bell.
S&P 500 futures were 7.20 points lower and were below 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 shed 46 points, and Nasdaq 100 futures slipped 7.50 points.
The benchmark S&P 500 has rallied 45 percent from the 12-year closing low of March 9 as investors bet on an economic rebound.
The Conference Board releases July consumer confidence figures at 10 a.m. (1400 GMT). Economists in a Reuters survey expect a reading of 49.0 compared with 49.3 in June.