This study aims to investigate the differences in learners’ English grammar achievement by an online asynchronous class group and face-to-face class group, preferred teaching method for English grammar items in the post-COVID era, and the learners’ perception of online asynchronous classes. To this end, 64 students from the online asynchronous class group and 46 students from the face-to-face class group, totaling 110 students were evaluated and surveyed. The results are as follows: First, the online asynchronous class group showed higher achievement than the face-to-face class group in most grammar items except for the type of verb, but there was no statistically significant difference. Secondly, about half of the respondents did not care about online and face-to-face teaching, but the grammar items of the respondents who chose more online asynchronous lectures were subject-verb agreement/tense/voice, noun/pronoun, and adjective/adverb. The appropriate number of online asynchronous classes for English grammar items was 3-5 times a semester, with 20 minutes being selected the most. This research has significance in that the findings can be used as a basic reference for the design and operation of hybrid online and offline English grammar learning.