Advance-Pierre Foods, a subsidiary of Tyson, is recalling more than 10 tons of ready-to-eat beef patties.
The US Department of Agriculture says the company received at least two consumer complaints about finding purple plastic in the food.
There are no reports of injuries or illness.
The patties in question were produced last November in Oklahoma and were distributed to schools nationwide.
The USDA says it did not provide the burgers as part of the national school lunch program.
Officials say anyone who purchased the patties should throw them out or return them to where they were bought.