We describe a system for parametric conversion of high-energy,Q-switched laser pulses from 1.064 microm to 2.1 microm in KTiOPO(4). High beam quality and efficiency are obtained by use of a two-stage system: An optical parametric oscillator (OPO) pumped by a narrow beam with 8 mJ of energy, generates 1.9 mJ of signal energy for seeding an optical parametric amplifier (OPA). With 500 mJ pump energy, different OPA configurations produce up to 138 mJ signal energy with M(2) approximately 2.3.