Working area and cost were discussed based on 3 composed mechanized equipment levels in case that a cooperative method for grass harvesting work will be used by several small scale dairy farms. Coverage and working cost for forage grass around Morioka city in a suitable harvesting period were calculated. Selection of grass harvesting system and its productivity were also discussed according to profitable working area by comparing the advantages in case of changing the annual working proportion of wrap grass silage and hay harvesting. The results are as follows.<br>1) For the same mechanized equipment level, the working cost of the hay harvesting system was lower than that of the wrap grass silage system. However, the difference of cost between the two systems decreased with increasing working area.<br>2) For the estimated working area based on the number of available working cycle in a suitable harvesting period for the forage grass around Morioka, the working cost was separated into grass cultivating cost and harvesting cost for discussion. Differences among the 3 mechanized equipment levels were small for the grass cultivating cost but large for harvesting cost at the same working area. Total working costs for the coverage of each mechanized equipment level were about 210, 000yen/ha.<br>3) The profitable working area of mechanized equipment I, II and III which are shown in Table 1 for the combination of the wrap grass silage (for first grass and third grass) and the hay harvesting (for second grass) were 9, 12 and 16 ha respectively. If the weather is good, it is more profitable to change the wrap grass silage method into the hay harvesting method.