Campbell Soup Co. made progress in its effort to reignite growth after a tumultuous year, underscoring the gulf between smaller food makers that reported earnings this week and the problems facing Kraft Heinz Co.

Campbell said on Wednesday that comparable sales were flat in the latest quarter as gains for Pepperidge Farm Goldfish crackers offset continued weakness in condensed-soup sales. However, Campbell’s gross profit margin slipped as it spent more on promotions for its brands and faced higher costs for transporting products....