In addition, quantities of tubers were trucked to the Shelley dehydration plant across the river in Burley. Large storage facilities were built at the Heyburn site for both raw potatoes and frozen products.

As well planned and managed as the system was it became obsolete with the tremendous growth in the frozen potato industry that took place in the 1975 to 1985 period. Frozen French fries, particularly for the foodservice market, became the dominant product. Becoming a major supplier of frozen French fries for the McDonald's chain of fast-food restaurants, and supplying other major chains, as well, dictated huge expansion by Simplot in frozen production capacity. Potato wastes were utilized for livestock feed and, more recently, for the production of ethanol. The economics of supplying the growing French fry market led to the Simplot Company becoming specialized in frozen-potato production and discontinuing dehydrated products, an area in which it had been a pioneer.

A growing market for frozen potato products made it necessary for Simplot to increase production capacity. In 1973, plants built by other companies were purchased by Simplot in Crookston, Minnesota, Idaho Falls, and Aberdeen, Idaho. In 1977, the company built a frozen-processing plant at Hermiston, Oregon, and purchased a processing facility at Grand Forks, North Dakota.

The J. R. Simplot Company participated in the development of the Automatic Defect Removal system, which greatly reduced trim-table labor, and in the use of railroad cars refrigerated with liquid carbon dioxide for shipping frozen foods. The company also built a $6 million research and development center at the Caldwell plant site.

In the early 1990s, the growth in domestic sales of frozen French fries has slowed. Existing plants are adequate to supply demand. The popularity of pizza restaurants and ethnic foods has slowed the increase in frozen French fry consumption.

To continue growth, the Simplot Company has looked elsewhere. New frozen products, including flavored French fries and curly cuts have helped, and more recently frozen mashed potatoes have been introduced.