This research was conducted on rice paddy area at the Simarasok Village, West Sumatra Province, Indonesia, aimed at investigating the effect of dosage of cow dung as organic fertilizer on growth, yield component and production of organic rice. The experiment was arranged using a Complete Randomized Block Design with four treatments and six replications. The treatment was organic fertilizer of cow dung composted using local microbial organisms with four dosage levels, namely: a) 2 tons/ha; b) 4 tons/ha; c) 6 tons/ha; and d) 8 tons/ha. The rice variety used was the Kuriak Kusuik and the observed variables included: leaf color score, plant height, maximum number of tillers, number of productive tillers, panicle length, number of grains per panicle, percentage of empty grain, weight of 1000 grains, and grain yield. The result showed that the dosage of organic fertilizer of cow dung had significant effect on leaf color score at 56 days after planting (DAP), number of productive tillers, number of grains per panicle, and grain yield. In contrast, plant height, maximum number of tillers, panicle length, weight of 1,000 grains, and empty grain were not significantly affected. It was found that there was a positive relationship between the dosages of organic fertilizer of cow dung with the grain yield. The addition of cow dung as the organic fertilizer as much as 1 ton/ha to the soil could cause an increase in the yield of grain by 0.097 ton/ha.