We investigate the effects of viewing conditions and rotation methods on different types of collaborative tasks in a two-user colocated tabletop augmented reality (AR) environment. The viewing condition means how the manipulation of a tabletop world by one user is shown in the other users' views and the rotation method means what type of input devices is used to rotate the tabletop world for alternative orientations. Our experiment considered two viewing conditions (consistent view and inconsistent view), two rotation methods (direct turn and indirect turn), and two task types (synchronous and referring-strong type, and asynchronous and orientation-strong type). A 3D display environment called "Stereoscopic Collaboration in Augmented and Projective Environments (SCAPE)” was utilized as a test environment. According to the results, the viewing conditions had significant effects on several objective and subjective measurements. On task completion time, their effect for the synchronous and referring-strong type of task was opposite to that for the asynchronous and orientation-strong type of task. On the other hand, the rotation methods had significant effects only on the accumulated turn angle (for both task types) and the number of negotiation phrases (only in the inconsistent viewing condition for the asynchronous and orientation-strong type of task).