In order to determine the nature of naturalistic learners' difficulty with grammatical gender in a complex morphological system, the longitudinal production data of an early naturalistic L1-Italian and L1-Turkish learner who are acquiring German are examined in light of current theories of gender within Chomsky's (1995) Minimalist Program. After analyzing the speakers' marking on determiners, adjectives and pronouns, we conclude that these learners' errors in the gender of German nouns are the result of at least four factors: inadequate lexical learning, mapping difficulty, processing pressure, and parsing errors that cause the paradigm to be inadequately learned. These factors may be particularly problematic for learners acquiring a system such as the one in German, where gender marking is conflated with case and number on determiners, adjectives and pronouns.