* Weight Watchers soars after Oprah takes stake
* China Q3 GDP data better than expected
* Futures down: Dow 56 pts, S&P 7.5 pts, Nasdaq 14.5 pts
By Abhiram Nandakumar
Oct 19 (Reuters) - U.S. stocks were set to open lower on Monday after weak results from Morgan Stanley added to investor concerns about U.S. corporate health.
Morgan Stanley's shares fell 5.2 percent to $32.18 premarket after the bank's profit fell for the second straight quarter.
The bank's results capped mostly downbeat quarterly results from major U.S. banks with struggling trading businesses.
Investors will continue scrutinizing company reports this week with several Dow components posting quarterly results, including Caterpillar, Boeing, Amazon and Coca-Cola.
"After three weeks of market gains, any disappointing earnings this morning could indicate that we could be in for some profit taking," said Peter Cardillo, chief market economist at Rockwell Global Capital in New York.
At 8:23 a.m. ET (1223 GMT), S&P 500 e-minis were down 7.5 points, or 0.37 percent, with 137,958 contracts traded. Nasdaq 100 e-minis were down 14.5 points, or 0.33 percent, on volume of 23,367 contracts. Dow e-minis were down 56 points, or 0.33 percent, with 20,344 contracts changing hands.
U.S. stocks closed higher on Friday, gaining for the third straight week. The S&P 500 marked its longest winning streak since May.
Halliburton fell 0.8 percent to $37.49 after the oilfield services provider posted a quarterly loss, hurt by charges related to asset write-offs and severance costs.
S&P 500 companies are expected to show a 3.9 percent fall in third-quarter profit, according to Thomson Reuters data.
Data on Monday showed China's economic growth slowed to 6.9 percent between July and September, but still ahead of the 6.8 percent forecast.
Reactions were mixed with most global markets rising as the data suggested that China may need more stimulus measures from Beijing though its economic health was not as bad as expected.
Brent crude oil prices fell below $50 a barrel on worries about demand from China and a global supply glut curbing Saudi exports.
IBM reports quarterly results after the close.
Data on U.S. homebuilder sentiment is due at 1000 ET (1400 GMT). The NAHB/Wells Fargo housing market index is expected to remain steady at 62 in October.
Federal Reserve of Richmond President Jeffrey Lacker, Chicago Fed President Charles Evans and Fed Board Governor Lael Brainard are scheduled to speak on Monday.
Valeant Pharma's U.S.-listed shares fell 1.5 percent to $174.98 after the drugmaker reported a better-than-expected quarterly profit.
PMC-Sierra jumped 12.8 percent to $11.55 after the chipmaker received a buyout offer from Microsemi, valuing the company at $2.4 billion.
Weight Watchers surged 70.1 percent to $11.55 after it said Oprah Winfrey will buy a 10 percent stake in the company and join the board. (Reporting by Abhiram Nandakumar in Bengaluru; Editing by Don Sebastian)