This study investigated age differences in the way in which attentional resources are allocated to expository text and whether these differences are moderated by content preexposure. The organization of the preexposure materials was manipulated to test the hypothesis that a change in organization across two presentations would evoke more processing effort (i.e., a "mismatch effect"). After preexposure, reading time was measured as younger and older adults read a target text to produce recall, answer comprehension questions, and solve a novel problem. Relative to the young, older readers allocated more time as they encountered new discourse entities and showed a stronger serial position effect, which are patterns of resource allocation that suggest more extensive processing of the discourse situation. Younger adults took advantage of repeated exposure to produce more extensive reproduction of text content, as well as more text-specific solutions to solve a problem. Older adults generated more elaborated inferences and were similar to young adults in terms of the dimensional complexity of problem solutions. Whereas younger readers showed weak evidence for a mismatch effect, older readers did not. These data are consistent with the proposal that older readers favor the situation model over textbase content in allocating resources to text, but this effect was not enhanced by introducing organizational difficulty in reprocessing. (Contains 6 tables and 3 figures.)