The present study explores the initial stages of incidental acquisition of two grammatical properties of verbs (subcategorization and [ir]regularity) during reading in first language (L1) and second language (L2) German using an adjusted self-paced reading paradigm. The results indicate that L1 speakers are superior to L2 speakers in the incidental acquisition of grammatical knowledge (experiments on subcategorization), except when the new knowledge interferes with previously acquired knowledge and mechanisms (experiments on [ir]regularity): Although both populations performed equally well regarding the acquisition of the subcategorization of verbs from the input (i.e., whether the verbs are transitive or intransitive), they differed with respect to the regularity status of new verbs. L1 speakers (in contrast to L2 learners) seem to disprefer irregularly conjugated verb forms in general, irrespective of their conjugation in the previous input. The results further show that the syntactic complexity of the context and morphological markedness positively affect the incidental acquisition of new words in the L2, triggering learners' shift of attention from the text level to the word level.