Stability of grain yield in upland rice due to the unpredictability of environmental indices is of important consideration in the development of cultivars adapted to fairly wide cultivation zone. A study was conducted with fifteen upland rice varieties in two locations in South-Western Nigeria to evaluate the contribution of panicle and grain characters to stable grain production. Data collection spanned five environments and was subjected to stability analyses. The effects of genotype, environment and their interaction were significant for all the panicle and grain characters. Broad sense heritability estimate (HB) was moderate for hundred grain weight (62.4) and grain length (58.9) but was generally low for other grain yield traits, particularly grain weight per panicle (11.6) and grain weight per plant (5.6), respectively. Stability variance identified different genotypes as stable for most of the characters. The crossover attribute of AMMI PC 1 however complimented the significant verdict returned by the stability variance though the former also specified the direction of instability. The Yield Stability index (YSi) harnessed the advantages of the two statistics to identify different genotypes as stable for different characters. Thus, there is a need to constitute a pool of genotypes for the evolution of superior synthetic but stable cultivars.