Structured AbstractPurpose: To empirically investigate the impact of: institutional pressures; institutional logics; and institutional complexity; on Sustainable Supply Chain Management (SSCM) practices across mixed public and private sector supply chains.Design/methodology/approach: Multi-case study data was collected from three tiers of food and catering supply chains: the customer/consumer tier; focal public sector UK Universities; and private sector suppliers / contractors. Findings:The findings indicate that: normative and mimetic pressures are more prevalent in focal Universities, compared to suppliers; there is typically no single dominant logic across these supply chains; and the multiplicity of institutional logics (e.g., sustainability logic versus financial logic) increases institutional complexity. Therefore, in the atypical case of homogeneity in terms of institutional pressures and logics, e.g. with a dominant sustainability logic throughout the supply chain, radical change in SSCM practices is facilitated. In contrast, in the more typical case when there is heterogeneity, with competing logics at different supply chain tiers, this limits SSCM to more incremental changes in practices. Research limitations/implications:This study is limited to three tiers of the food and catering supply chains of UK Universities. Practical implications:To aid in the successful implementation of SSCM, this study suggests a need for managers to develop an initial understanding of the prevailing institutional logics and pressures at different tiers of the supply chain. Social implications:A number of the SSCM practices studied address social sustainability. Originality/value:No previous studies have empirically investigated the impact of institutional complexity in the context of SSCM practices across supply chains, involving both mixed public and private sector organisations.

Sustainable supply chain management practices can be particularly difficult to implement when the responsibility for sustainable procurement (SP) rests with buyers employed by a contractor, rather than an in-house procurement team. Yet there is no extant research that investigates the effect of outsourcing on SP. To address this research gap, this paper uses multi-case study data to explore the impact of outsourcing versus in-house implementation modes in the pursuit of SP.The findings suggest that each implementation mode has distinctive challenges and facilitators. However, by considering Transaction Cost Economics, results reveal that the advantage of outsourcing to professionals, with well-established SP expertise, brings information asymmetries in developing initial outsourcing contracts, which can lead to poorer sustainability performance than initially expected. Furthermore, when applying Principal Agency Theory, results suggest that sustainable performance can be improved in the long term through the effective design of well-constructed contractual relationships as SP maturity increases.