The tech-rich Nasdaq Composite Index jumped 39.72 points (0.84 percent) to 4,796.25.
The Dow Jones Industrial Average rose 76.83 (0.47 percent) to 16,330.40, while the broad-based S&P 500 added 10.25 (0.53 percent) at 1,952.29.
Apple powered up 2.2 percent a day after unveiling a spate of new and upgraded smartphone, tablet and television products. Biotech stocks like Gilead Sciences (+3.3 percent) and Biogen (+3.0 percent) were also big gainers.
Charlie Bilello of Pension Partners said investors increasingly believe the Fed is unlikely to make the leap to raise zero-level benchmark interest rates at its policy meeting next Wednesday and Thursday.
"There's increasing hope that they're not going to do anything," he said. "My view is that they're not data-dependent, they're stock market-dependent."
Besides Apple, strong performers in the Dow included pharma giants Merck (+1.5 percent) and Pfizer (+2.1 percent).
ZS Pharma, a much smaller biopharmaceutical company, shot up 28.6 percent after Bloomberg reported it had been approached by Switzerland-based Actelion in a deal that would value ZS at about $2.5 billion.
Snack-food giant Mondelez International climbed 0.9 percent as it confirmed that it expects organic net revenue growth of at least three percent in 2015. It also announced plans to lift the share of revenues from healthy snacks to 50 percent by 2020.
Yoga-attire maker Lululemon Athletica tumbled 16.4 percent after it projected 35-37 cents per share in third-quarter earnings, well below the 43 cents expected by Wall Street analysts.
Cybersecurity company Palo Alto Networks rose 7.4 percent as it forecast sales of $280-$284 million for the current quarter, more than the $269.7 million expected by analysts.
Trucking and logistics company Con-way shot up 33.8 percent on news it will be acquired by rival XPO Logistics for $3.0 billion. XPO fell 11.0 percent.
Bond prices fell. The yield on the 10-year US Treasury rose to 2.23 percent from 2.19 percent Wednesday, while the 30-year advanced to 2.99 percent from 2.95 percent. Bond prices and yields move inversely.