Entrepreneurial growth—firm growth via the introduction of new market offerings or expansion into new markets—is an important topic for entrepreneurship scholars and practitioners alike. Any firm that wants to exploit opportunities for entrepreneurial growth needs resources and capabilities that it can use to develop new market offerings or to enter new markets. However, many firms face resource and capability constraints, and research has shown that strategic partnerships can provide external pathways for firms to exploit growth opportunities despite their resource and capability constraints. All the extant external growth pathways have in common that they require firms to have some resources and capabilities, which are valuable for partners and can be jointly appropriated with them. An alternative pathway for firms to leverage external resources and capabilities—especially knowledge-based ones—that has received little attention in the literature on growth is short-term contracting of professional service firms such as accounting firms, marketing agencies, or R&D consultancies. Hence, we investigate the role of service intermediaries—professional service firms that facilitate the exchange of services among other firms—as external managers who support their clients to access and leverage a broad range of required resources and capabilities from third parties. We conducted a nested multi-case study of two service intermediaries that enabled two small, wineries from North Macedonia to successfully seize entrepreneurial growth opportunities in markets abroad despite their resource and capability deficits. We identify seven support mechanisms—need articulating, social embedding, linking, governing, clarifying, renegotiating, and mediating—through which the service intermediaries orchestrated complementary external resources and capabilities on behalf of the wineries, thereby enabling the two firms to successfully develop two new product lines for and enter two new geographic markets each. We also identify process differences depending on the stage of the opportunity evaluation process, target market characteristics, and external stakeholder involvement for which we postulate three propositions about the influence of mechanisms on the growth opportunity development. Our study offers novel insights and makes a contribution to research on entrepreneurial growth and resource orchestration. Plain English Summary: Many firms face resource and capability constraints that inhibit their entrepreneurial growth. One approach that firms can use to overcome these constraints is by leveraging external resources and capabilities. However, constrained firms often are unable to establish relationships with and leverage resources and capabilities from external providers. Our study demonstrates how service intermediaries can orchestrate the complementary external resources and capabilities of constrained firms to enable the exploitation of growth opportunities in new markets. The findings of our study can provide policymakers, especially ones focused on regional competitiveness and economic growth, with a framework to foster the creation of intermediaries, which in turn can enable resource- and capability-constrained firms to exploit growth opportunities. In addition, constrained firms may use our findings of this study as a guiding framework when leveraging complementary external resources—independent of whether they orchestrate these resources themselves or engage external resource orchestration managers. [ABSTRACT FROM AUTHOR]