Stocks began lower, but pushed into positive territory for a time after Powell reiterated the need to counter inflation, but added that a recession was "certainly a possibility" amid the ongoing interest rate hikes.
Fears of a downturn were a driver of the oil market, which fell sharply, a move that has helped gasoline prices retreat a bit in recent days from record highs.
The Dow Jones Industrial Average dropped 0.2 percent to end at 30,483.13.
The broad-based S&P 500 dipped 0.1 percent to close at 3,759.89, while the tech-rich Nasdaq Composite Index declined 0.2 percent to 11,053.10.
Although stocks ended lower, Art Hogan, strategist at National Securities, said the session should be seen as "more of a victory" in that equities were able to retain most of Tuesday's gains.
Among individual companies, Kohl's fell 8.8 percent after a report on CNBC that Franchise Group is considering a lower bid for the retailer as it weighs a takeover offer.
Netflix jumped 4.7 percent following a report in the Wall Street Journal that the company was considering a venture with either Comcast's NBC Universal or Google-parent Alphabet on a lower-priced streaming service with ads.
Comcast rose 1.1 percent and Alphabet was flat.
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