Investors can thank strong earnings, rate cuts, and market-wide optimism for an unseasonably strong September and S&P 500 mere points from new record highs. But before investors stroll into the historically strong fourth quarter, it might be worth taking score of the stocks that made the index’s banner performance possible.
You might thank the mega caps which are dominating the market narrative: players like Nvidia (NVDA) , Alphabet (GOOGL) , and Meta (META) , to name a few. Credit to these firms: they’re among the largest holdings in the index for a reason, but there’s more than what’s happening at the top.
In fact, many of the middling holdings in America’s most-watched indexes put up fantastic showings in the third quarter. Here are a cropping of the best-performers from these record-setting three months:
Western Digital
AI investments aren’t just benefiting chipmakers like Nvidia NVDA, cloud giants like Oracle ORCL, and hyperscalers like CoreWeave CRWV. In fact, by many accounts, the biggest beneficiaries this year have been storage companies like Western Digital (WDC) .
The firm, which makes hard storage disks, has become the S&P 500’s second best-performing stock this year, rising 87.6% in the third quarter and bringing its year-to-date return to 168.46%. In fact, it’s second to only one other stock (which is also on the list below).
Much of that growth has come amid robust growth, mostly driven by data center buildouts, which are seeing hyperscalers and cloud giants purchase larger hard disks. The company’s fiscal year 2025 revenues grew 51% to $9.52 billion. And revenue growth is expected to remain impressive, with the company forecasting the coming quarter’s revenue to grow 22%.
Warner Bros Discovery
HBO and CBS parent company Warner Bros Discovery (WBD) also boasted a fantastic quarter, rising 70.42% in the last three months.
Most of the entertainment giant’s gains have come off the backs of a planned breakup of the company’s legacy and streaming media platforms. It’s a move which has long been speculated and could free up the company to focus its efforts on legacy media and streaming in two separate businesses.
However, it’s also worth touching on the $380 billion elephant in the room: the rumor mill is overflowing with murmurs that competitor Paramount Skydance (PSKY) might make a bid for the company. Such a bid would be backed by one of the world’s richest men, a topic we tackled in recent weeks.
Seagate Technology
It turns out that there’s plenty of room at the top for another storage company and AI beneficiary. Seagate Technology (STX) rose 63.6% in the third quarter, thanks to many of the circumstances which buoyed competitor Western Digital (WDC) .
However, it’s doing one better than its competition. The company has become a quiet favorite, eclipsing retail favorites like Palantir Technologies (PLTR) and Micron Technology (MU) to become the best-performing stock in the S&P 500, up 173% year-to-date.
Corning
They’re famous for making the glass on your iPhone, but it turns out, they have more than Gorilla Glass to offer. Material sciences company Corning Incorporated (GLW) jumped 56% in the third quarter, buoyed by a double-digit EPS and net sales growth.
Core Sales grew 12% year-over-year, while Core EPS grew 28% over the second quarter, led by the company’s Optical Communications business. (Go figure, it turns out it’s an AI beneficiary, too.)
Its Hemlock and Emerging Growth Businesses (+31% YoY in Net Sales) and Specialty Materials (+9%) were also standouts for the firm in its latest quarter performance.
Teradyne
Recently featured in a Bloomberg article on AI trades, Teradyne (TER) has attracted a fervent crowd of investors. The company, which builds tools to test chips in manufacturing plants jumped 53% in the quarter. That helped put the stock back in the green, +9.3% year-to-date.
Honorable Mentions
Outside of the top five stocks, there are dozens of stocks which outstripped the index’s quarterly showing. Among them were chipmaker Intel (INTC) , which is in the midst of a rebound trade. It was joined by Paramount Skydance (PSKY) , mentioned above. And Invesco (IVZ) , Newmont Mining (NEM) , and Arista Networks (ANET) weren’t far behind.