This study aimed to examine Korean learners’ language development under four different learning conditions with the aid of input enhancement. Four types of learning conditions were carefully manipulated: (1) more incidental, (2) less incidental, (3) rule-search, and (4) instructed. The two incidental groups were told to understand the meaning of the passage, while the rule-search group was asked to find the embedded rule while reading. The instructed group received explicit rule instruction before the reading task. A total of 141 11th grade high school students in South Korea participated in this study and took pre/post grammatical judgment tests, a reading comprehension test, and a guided sentence composition test. The findings indicated that incidental rule learning in Korean EFL was possible while their attention was on meaning. In addition, the degree of rule learning and output was maximized when explicit instruction was presented. However, there was no significant difference in the participants’ overall reading comprehension. Along with pedagogical implications, the three interface positions are also discussed.