Interaction has received attention in different fields of applied linguistics. In the field of Second Language Acquisition (SLA), scholars have perceived interaction as a platform where L2 learners can engage in language experimentation. It has been considered in light of Long's (1981) Interaction Hypothesis, which posits that negotiation of meaning is the basis of L2 learning. Researchers also examined interaction from a different perspective, where they described salient features exhibited in different patterns of peer interactions to understand the underlying construct of conversation management in the context of L2 assessment (Galaczi, 2008). Previous studies that investigated L2 interaction mostly used qualitative methods over small datasets. The present study adopted a quantitative approach to understand the construct of interaction. To do so, L2 pair interaction was measured by creating a composite score of interactivity level to understand the relationship between students' degree of interactivity and their use of lexico-grammatical features as well as their L2 fluency. The study also examined the effect of tasks on L2 pair interactivity level. Pearson's correlation tests, as well as Spearman's rank correlation tests, showed that interactivity is associated with discourse particles, response forms, wh-questions, and second-person pronouns, while it was negatively associated with nominal forms (i.e., all instances of nouns, common nouns, and the length of the word) and hesitators. Furthermore, the results showed that interactivity was associated with more fluent L2 talk, where students of higher interactivity levels tended to produce faster speech rates and fewer silent pauses. Additionally, an ANOVA test showed a large effect of task on L2 interactivity. Further analyses suggested that the general communicative purpose of task has a limited effect on L2 pair interactivity. However, the task prompt showed patterns that relate the type of information (e.g., lists of sentences, scientific graphs, words/phrases, images) provided to students in the prompt to patterns of L2 interactivity levels. The study provides insightful information for scholars interested in L2 interaction in oral assessment and L2 dialogic tasks. [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.]