This paper examines the behavior of a labor-managed income-per-member-maximizing firm and a profit-maximizing firm in a quantity-setting model with a strategic commitment. First, each firm independently decides whether or not to make a commitment to capacity. This capacity may subsequently be increased, but cannot be decreased. Hence, each firm's investment choice changes its capital cost from a variable one into a fixed one. Second, each firm independently chooses its actual output. The paper examines the equilibrium of the quantity-setting mixed model and shows whether or not capacity investment is effective for the labor-managed firm and the profit-maximizing firm. (C) 2008 University of Venice. Published by Elsevier Ltd. All rights reserved.