In an attempt to explore the effects of overseas language programs on learning English grammar, the present study investigates English grammar used by Korean university students who joined an overseas language training program for a semester. 27 students participated in a semester-long exchange student program at a university in the Philippines. For data collection, pre- and posttests were conducted at the beginning and at the end of the semester. Written data collected were analyzed before and after the treatment period to discern differences in the use of three grammatical items (infinitives, verbs, and participles), and statistical analyses were carried out. The results showed that the students as a whole gained lexical fluency, producing longer sentences embedded with a larger number of words in more complex structures after studying abroad for a semester. Also, a higher frequency in the usage of the grammatical items was observed despite an increase in the number of errors in syntactic and lexical use. It was revealed that while the students attained control over morphological items, their grammatical accuracy in syntactic and lexical use showed no significant improvement during a semester abroad.