Poly(L-lactic acid) (PLLA) is the most promising bio-based thermoplastic polyester with high mechanical properties, positive life cycle and low-cost production from renewable raw materials. Although PLLA is suitable for short-term packaging, specific properties are required to reach high-value applications, such as a high thermal resistance and long-term durability. Therefore, binary PLLA / PMMA and ternary PLLA / PDLA / PMMA blends are investigated. When melt-processed via extrusion, only miscible PLLA / PMMA blends were recovered, marked by a homogenous morphology and a high transparency. Tunable glass transition temperature, a-relaxation temperature, thermal resistance and gas permeability arise from the miscibility with promising performances for durable and technical applications. However, PLLA crystallization is seriously inhibited and only quasi-amorphous blends could be produced by injection-molding. Ternary PLLA / PDLA / PMMA formulations were also found to be miscible in the melt state and, surprisingly, the amount of PLA stereocomplexes formed during high-speed cooling is significantly enhanced with 30 – 40 % PMMA. In addition, comparative thermomechanical analysis reveals a dual reinforcment of the storage modulus and of the thermal resistance, especially for ternary formulations with 40% PMMA. Finally, highly-crystalline blends were easily recovered after thermal annealing. PLA stereocomplexes exclusively crystallize and these nearly-transparent materials present an impressive evolution of the thermomechanical properties, with a tan d peak at 106°C. By using a simple and robust twin-screw extrusion process, the introduction of PMMA into poly(lactides) matrices could efficiently overcome actual limitations of poly(lactides) in terms of thermal resistance, crystallinity and processability. Consequently, the use of PMMA is found to play a key role for the introduction of poly(lactides) into technical and durable applications.