This study was inspired by VanPatten and Uludag’s (2011) study on the transferability of training via processing instruction to output tasks and Mori’s (2002) work on the development of talk-in-interaction during a group task. An interview was devised as the pretest, posttest, and delayed posttest to compare four intervention types for teaching the simple past passive: traditional intervention as the comparison group and three task-based groups were processing instruction, consciousness-raising, and input enhancement. The interviews and the interactions during the treatments were also analyzed qualitatively. Task-based instruction (TBI) proved significantly more effective than traditional intervention and processing instruction significantly outperformed all others on both posttests. Furthermore, processing instruction was the only task-based intervention to retain its improvement till the delayed posttest. Qualitatively, processing instruction led to true negotiation of meaning and deep-level learning, consciousness-raising led to massive negotiation over the function of the target structure and deep-level learning, input enhancement led to enormous unfocused interaction about meaning, and traditional intervention just led to interaction about the forms. It was concluded that a well-planned processing instruction is a promising intervention for focusing on language form; however, due to the strong points cited for the other two tasks, their roles should not be ignored.
