A bale chamber 22 includes a pair of elongated top rails 72,74, a pair of elongated bottom rails 80,82, an elongated right siderail 80, an elongated left siderail 90, and a squeeze mechanism 24 positioned proximate the discharge end of the bale chamber 22 for symmetrically adjusting the cross-section size of the discharge opening by simultaneous movement of all the rails. The squeeze mechanism 24 includes a vertical squeeze assembly 92 for adjusting the vertical distance between the top and bottom rails 72,74,80,82 and a horizontal squeeze assembly 94 for adjusting the horizontal distance between the left and right siderails 88,90. Each squeeze assembly 92,94 includes a jaw-type lever assembly 96,116 surrounding its respective rails and a cylinder assembly 98,118 that selectively shifts its lever assembly 96,116 and its respective rails towards and away from one another near the discharge end of the bale chamber 22.