The Open Innovation (OI) paradigm has emphasized the role of external knowledge in aiding internal R&D efforts. While most research based on this model has focused on high-tech sectors, this paper attempts to extend it to more mature industries. The study also analyzes a wide range of OI strategies and their relationships with different innovation outcomes. The empirical results, based on a large sample of Spanish manufacturing firms, show that OI strategies are highly effective tools for making internal R&D efforts more successful, both in high- and low-tech sectors. In addition, the study finds evidence that marketbased strategies are positively correlated to achieving process innovations, while partnering strategies have a similar relationship with product innovations. More formalized OI strategies, such as joint ventures, show positive relations with the achievement of patent results.