Coops are socio-economic organizations established to meet the common needs of members. In Ethiopia, the establishment of coops dates back to 1960s. However, during the successive periods different parties with distinct social, political and economic ideologies contrary to the principles of coops ruled the country. Above all, forced formation of coops during the Derg regime perpetually limits participation in coops. Previous studies also confirm that the member initiated only 26% of the coops. It was after 1991, the economic liberalization policies have been effective in realizing the economy from state control, in Ethiopia, which includes also reevaluation of the role and structure of Coops. In the coffee marketing activities it was after the issuance of Pro. No. 147/1998, several coffee farmer coops union have been established. YCFCU is among these unions established to support smallholder coffee farmers who lack bargaining power. In light of the participation problems this monograph is an empirical investigation aimed at understanding the determinant factors of members marketing participation in coffee marketing coops.