Activist investor Starboard Value has built a sizable stake in Lamb Weston, the frozen-potato products maker, and is pushing for faster improvements and cost-cutting to boost the company's underperforming stock, according to people familiar with the matter. Lamb Weston produces french fries, hash browns, and other frozen potato products, counting major fast-food chains like McDonald's among its customers.

Starboard is now one of Lamb Weston's largest shareholders, though the exact size of the firm's stake couldn't be determined. The activist investor's move comes as Lamb Weston's stock has struggled to meet performance expectations, prompting calls for operational improvements and strategic changes. The company's frozen potato products are sold to restaurants and retailers worldwide.

The activist's involvement signals growing pressure on Lamb Weston to enhance shareholder value through cost efficiencies and potential strategic shifts. Starboard's track record of pushing for operational improvements at portfolio companies suggests Lamb Weston may face demands for changes in its business strategy and cost structure.