To help constrain the rheology of and strain partitioning in composite silicates from lower continental crust (LCC), opx-hbl-plag granulite samples were shortened coaxially 15-40% in a solid pressure medium (NaCl) apparatus at P c = 1.0 GPa, T = 650-950°C, and strain rates from 10 - 5 to 10 - 7 s - 1 . The resultant mechanical behaviour and microstructures are compared with those of Pikwitonei amphibolite (58% hbl, 42% plag) deformed by Wilks and Carter (1990) under similar conditions. The opx-hbl-plag rock is stronger than the hbl-plag rock at all conditions. All samples strain soften beyond 10% strain and stress levels do not reach steady state once softening begins. At low T and high strain rates, relative mineral strength is plag opx hbl, whereas at higher T and lower strain rates relative mineral strength is opx plag < hbl. Opx grains are extensively kinked by glide on (010)[001] at all conditions, plagioclase deforms by translation glide and mechanical twinning that becomes more abundant with higher T, and amphibole deforms by slip on (100)[001]; microcracking in all phases partially accommodates strain under all conditions. Recovery mechanisms are limited even at the highest temperature and lowest strain rates. Tubules along grain boundaries and within grains suggest that a fluid phase, possibly related to amphibole breakdown, was present during experiments. Semibrittle shear zones (SSZs) comprising S-C fabrics defined by elongate grains of all phases develop in all samples; SSZs initiation coincides with the onset of mechanical softening. SSZs initiate along grain boundaries and widen with increasing strain, which accounts for progressive softening with time. Similar S-C fabrics have been duplicated in simple shear tests under indentical conditions which, in turn, are comparable to fabrics in naturally deformed LCC rocks. Increasing the number of co-existing hard phases in natural composite silicates promotes strain localisation by enhancing ductility contrast(s) between constituent phases.