In this work we propose the use of Entropy to measure variability in pronunciations in pseudowords reading aloud: pseudowords where participants give many different pronunciations receive higher Entropy values. Monolingual adults, monolingual children, and bilingual children proficient in different European languages varying in orthographic depth were tested. We predicted that Entropy values will increase with increasing orthographic depth. Moreover, higher Entropy was expected for younger than older children, as reading experience improves the knowledge of grapheme-phoneme correspondences (GPCs). We also tested if interference from a second language would lead to higher Entropy. Results show that orthographic depth affects Entropy, but only when the items are not strictly matched across languages. We also found that Entropy decreases across age, suggesting that GPC knowledge becomes refined throughout grades 2-4. We found no differences between bilingual and monolingual children. Our results indicate that item characteristics play a fundamental role in pseudoword pronunciation variability, that reading experience is associated with reduced variability in responses, and that in bilinguals' knowledge of a second orthography does not seem to interfere with pseudoword reading aloud.