We describe the design and development of a technology-based inference-making intervention system that includes a set of interactive learning modules, each of which engages students to (a) view age-appropriate children's videos, (b) learn vocabulary words that are central to main ideas in each video, (c) respond to inferential questions, (d) receive scaffolding and specific feedback for each question, and (e) engage in a set of read-aloud lessons implemented by the classroom teacher and designed to promote transfer of inferencing from non-reading to reading contexts. First, we present the design principles that guided development, drawing on an integrated language comprehension framework. Next, we describe the design process, drawing on a field test of the usability and feasibility of the intervention system. Findings revealed that students and teachers found the system to be usable and helpful for support inference-making, and that it was feasible for classroom use. Then, we provide evidence from a field trial that showed that children who used the intervention system made gains in language comprehension, and that a version with 'offline' questioning (questions asked after viewing videos) was slightly superior to an 'online' version (questions asked during viewing). Finally, we highlight lessons learned that are informing additional development. [This paper will be published in "L1-Educational Studies in Languages and Literature."]