Studies have demonstrated that young readers can integrate information across texts. However, the literature on the online processes of young readers during multiple-text reading is limited. The present study uses children’s vocabulary ability as a covariable to investigate how they process information across texts and to determine how multiple-text reading differs from single-text reading in terms of eye-movement control, lexical access, subsequent integration, and macro-integration. For this study, we ensured that the texts used in the single-text and multiple-text reading scenarios were equivalent; for the multiple-text reading scenario, participants read a first text followed by a second text. Five sets of Traditional Chinese texts were used in this study, with each set comprising two expository texts centered on a common topic. The two texts in each set did not present conflicting information. Instead, the information in the second text expanded on the information in the first text. To create texts suitable for elementary school students, the text structures of all 10 experimental texts in addition to their word-level characteristics and article length were standardized. The results of this study indicate that the tested fourth-grade children could adjust their reading strategies spontaneously, depending on whether they were engaged in single-text reading or multiple-text reading. Regarding the role of vocabulary during multiple-text reading, we discovered that the fourth graders with higher vocabulary proficiency exhibited increased engagement in lexical processing and macro-integration when they were reading the first and second texts, respectively. By contrast, the fourth graders with lower vocabulary proficiency exhibited less engagement in lexical processing while reading the first text and were less likely to reread the second text. The fourth graders with higher vocabulary proficiency were more inclined to adjust their reading strategies depending on the text they were reading, whereas those with lower vocabulary proficiency were more inclined to adopt a minimalist strategy. We discussed these findings in relation to current models of multiple-text comprehension and explored their educational implications.