Variability in oral reading fluency (ORF), an indicator of foundational reading skills, has been linked to characteristics of texts. Such "text-based variability" in ORF has been traditionally attributed to text complexity, but substantial text-based variability has still been observed after accounting for text complexity. We consider that "oral" reading requires pronouncing the text aloud, which makes it subject to the same articulatory and prosodic constraints as other types of speech productions. Thus, texts with similar levels of complexity may still differ in expected durations when read aloud because of the texts' segmental and prosodic structure, leading to differences in reading rate. We propose that these "production-related effects" are also important sources of text-based ORF variability. Data from upper elementary school students in the United States reading a large variety of passages from a popular fiction book showed that a composite measure of production-related effects (i.e., reading rate estimates derived from a text-to-speech synthesis system) explained a substantial amount of text-based ORF variability. Follow-up exploratory analyses indicated that these production-related effects are robust. Because text complexity metrics consist of features that also tap into production constraints, our results motivate an updated interpretation of text complexity effects on ORF and highlight the importance of accounting for production-related effects on ORF, which remain to be acknowledged in the ORF literature as potential sources of text-based variability.