Foodstuffs were stored in the granary for distribution to the village people.  Prior to the coming of the Spanish, the Pima diet consisted of squash, beans, corn, small game, and wild plants.  The Spanish brought sheep, goats, and cattle, adding protein to the diet.  They brought wheat, which could be grown in winter, as well as fruit trees, such as apricot, fig, apple, and pomegranate, providing a pleasing dietary variety.

The stairs led to a loft where extra food and animal fodder were stored when the granary was in use.  The food was kept in baskets and clay pots for later distribution.  The mission was a communal system of growing, collecting, and distributing.

How were fruits, fleshy foods and meats preserved without refrigeration or canning?  Extensive use of the hot desert sun and dry climate was made in preserving many foods for year-round use.  Fruits, meat, and grains were all dried before placing them in their respective containers to be used during the non-growing season.

The granary is the only known, two-story auxiliary building in the mission complex.  Holes in the walls for vigas, horizontal beams of mesquite or cottonwood, mark an upper story.  A stairway and vestibule divide the ground floor into two rooms; no evidence exists for an upper story partition.  One prominent room feature is a bench with 13 circular depressions believed to be pot rests.