Abstract: A system and method for co-localizing temporally accessed data is provided. In one embodiment, objects having a plurality of fields are reorganized. A subset of the fields in an object are each associated with an access frequency that is determined by the number of times the corresponding field is referenced by a program module. The fields within an object are periodically reorganized to form a reorganized object in which frequently accessed fields are co-localized. Further, references to the object in the calling program are updated to properly reference the reorganized object. In another embodiment, objects in a memory that are temporally accessed by a program module are identified as temporally accessed groups. Each temporally accessed group is transferred to a destination space and marked. Then, in a Cheney-style approach, objects that comprise the program roots of the program module are transferred to the destination space.