Participatory organizational wellbeing interventions (POWIs) are increasingly used to address complex and persistent challenges to employee wellbeing by involving organizational members in the design and implementation of change. Yet their longer-term outcomes vary widely, raising questions about how organizational members make sense of such interventions at the point of design and enactment. This paper adopts a prospective sensemaking perspective to explain how POWIs may contribute to organizational change capability over time. Drawing on sensemaking theory, schema theory, and organizational memory, we conceptualize POWIs not merely as technical change mechanisms but as sensemaking infrastructures that shape how organizational members interpret, enact, and sustain wellbeing-oriented change. We develop a conceptual model centered on prospective sensemaking - the collective process through which organizational members construct forward-looking interpretations, imagine possible futures, and coordinate present action based on anticipated outcomes. We argue that prospective sensemaking during POWIs is grounded in organizational memory, understood as accumulated knowledge and experience from prior interventions and wellbeing initiatives. Organizational members interpret new intervention cues in relation to existing cognitive schemas, perceived source credibility, and the recency, relevance, and significance of past experiences, shaping the plausibility of intervention narratives and the dynamics of sensegiving. Building on this model, we advance five propositions linking interpretive cues, organizational memory, and collective sensemaking to the development of organizational change capability. We argue that when prospective sensemaking becomes collective and stabilized through shared meanings, POWIs are more likely to support enduring capacity for change. By theorizing the temporal and interpretive dynamics through which participatory interventions mobilize organizational memory to shape future-oriented action, this paper contributes to research on organizational wellbeing, organizational change, and sensemaking, offering a novel explanation for why some POWIs become embedded and sustained while others remain episodic.