In this study, the compressive creep behavior of La0.2Sr0.8Fe0.8Cr0.2O3-delta (LSFCO) in oxygen-controlled atmosphere is investigated in order to understand the underlying stress-induced cation diffusion and defect chemistry in this compound. The creep behavior is investigated in the stress, temperature and grain size ranges of 10-80 MPa, 1100- 1175 degreesC and 3.2-28.5 mum, respectively. The oxygen atmosphere is controlled in the oxygen partial pressure range of P-O2 = 0.21 - 10(-14) atm. The material exhibits two markedly different behaviors at high and low P-O2. At high P-O2, the behavior is characterized by the oxygen partial pressure exponent of m=0.04, followed by a drastic increase in strain rates at low P-O2, characterized by m = -0.5. In the m = -0.5 regime, the effect of oxygen partial pressure on the grain size exponent, as well as the transition to power-law creep is investigated. It is concluded that the mechanism responsible for the rapid increase in strain rates increases the contribution of bulk diffusion from predominant (p = 2.3) to nearly pure bulk diffusion (m = 2.07). The same mechanism also increases the stress range for predominant diffusion creep relative to power-law creep. (C) 2003 Elsevier B.V. All rights reserved.