The igneous protoliths of metamorphic rocks included in the Sardoal and Mouriscas Complexes, cropping out on the northeastern border of the Ossa-Morena Zone, are products of long-lasting heterogeneous partial melting of metasedimentary and meta-igneous crustal domains at different depths, conceivably related to a multistage continental arc development from at least ~570 to ~550/540 Ma. These rocks preserve evidence of a LP‒HT metamorphic event progressed under amphibolite or amphibolite-granulite transitional facies conditions dated at ca. 540 Ma, recording the continental arc accretion to the Iberian autochthon passive margin, and developing a Cadomian suture further reworked during the Variscan cycle. The mineralogical composition of migmatites suggest an heterogeneous process of decompression-driven crustal anatexis possibly concomitant of a rapid exhumation of basement rocks.