In this work, the effect of combinations of peats, which have different characteristics on mushroom yield and earliness, was investigated. The most important problem in mushroom cultivation is to obtain a suitable peat in Turkiye. It is necessary to find practical performance and proper combinational materials for casing. In the study, peats from 3 different locations, which are generally used by mushroom growers in Turkiye, were investigated. Peats were used in mixture of 25, 50, 75 and 100% v/v proportions of different peat sources. Mushroom was harvested daily, and the total yield of every seven days were evaluated, earliness and yield obtained during 21 days (three flushes) were tested as a total yield. The highest mushroom yield and earliness were obtained from rough and brown peat 25%+more decomposed and black peat 75% treatment.