What happened

BJ's Warehouse Club (NYSE:BJ) shareholders dramatically outperformed the stock market last month. The stock jumped 37% in May compared to a 4.5% increase in the S&P 500, according to data provided by S&P Global Market Intelligence.

The rally added to significant gains since the start of 2020, as the retailer's stock is up over 60%.

A woman examines packaged meat in a grocery store.

Image source: Getty Images.

So what

Investors applauded the chain's fiscal first-quarter earnings results, which showed booming sales growth through the early days of the COVID-19 pandemic in North America. The warehouse retailer said revenue jumped 27% at existing locations in the period compared to a 1% uptick during the prior full fiscal year. That result compared favorably to the 10% increase that Walmart's (NYSE:WMT) Sam's Club reported, and to Costco's (NASDAQ:COST) 8% boost.

Now what

BJ's had trailed these peers in prior quarters, so investors will be watching the next few earnings reports to see if the Q1 metrics represent a sustainable change in its market share trajectory. That's the surest way the consumer staples giant can improve its long-term profit potential while boosting shareholder returns at the same time.