Due to the typological differences between Korean's aspect system and English's aspect system in terms of progressive construction "-ko iss," learners can no doubt have difficulty acquiring and using the "-ko iss" construction in learner Korean. This dissertation investigates two main points: (i) how is the "-ko iss" construction used in real-world Korean, including L1 Korean and L1 English and L1 Japanese learner Korean, and (ii) the way "-ko iss" is taught and used in textbooks as a main source of input for learners of Korean. To answer these questions, I use collostructional analysis to assess association strengths between verbs and the "-ko iss" (progressive) and simple (non-progressive) constructions to identify verbs that are well-attested with L1 and L2 Korean. Finally, I take an exploratory approach to using logistic regression to model L1 and L2 Korean data, the results of which can provide some insights into L1-L2 "-ko iss" usage, and insights from this initial regression analysis provide meaningful information to improve modeling of L1 and L2 Korean in future studies. The main takeaways from this study are: (a) Verbs co-occurring with "-ko iss" in the written Sejong corpus included a wide variety of usage cases, including many instances of stative or mental-type verbs, including al (know), mid (believe), among others. (b) Verbs co-occurring with "-ko iss" in the learner data showed a positive sign in that learners use and acquire the "-ko iss" construction's various semantic meanings, including its use with stative verbs. However, semantic domains used with -ko iss are limited when compared with the L1 data. (c) In textbooks, a limited number of verbs is introduced with -ko iss at the beginner levels. "-ko iss" is also taught in textbooks as a prototypical action in progress progressive construction, without clear direction instruction on other senses of "-ko iss." Further, across both textbook series, the frequency -ko iss is used at is low (maximum around 300 occurrences in a textbook series). Textbooks incidentally use "-ko iss" outside of the prototypical action in progress usage at later levels, however, frequencies are quite low. Findings from this dissertation can be used to inform language pedagogy. The list of verbs co-occurring with the "-ko iss" construction from the collostructional analysis provides teachers and textbook developers with a list of attested to function with "-ko iss" across a variety of usages beyond action in progress. Plenty of examples are also pulled from the corpus for materials developers to reference when designing textbook materials. As the aim of language teachers and materials developers is to use data-driven insights to improve teaching materials, exposing learners to a variety of verbs within contexts or lexical chunks they appear in via textbooks can aid in learning complex constructions in Korean. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]