The paper examines covert restructuring in the tense-aspect system of heritage Russian—a systematic grammatical reorganization that distinguishes advanced heritage speakers of Russian from monolingual speakers in the absence of overt errors. Quantitative experimental data is provided on the occurrence of grammatical tense and aspect markers in compositionally telic and atelic contexts, with a special focus on aspectually transient predicates (activities and accomplishments), known for their variable telicity effects. The results suggest that particular properties of verbal arguments, such as the expression of quantity on the direct object, trigger systematic patterns of morphological variability in the encoding of temporality in heritage Russian, both in the domain of verbal aspect and tense. For aspect, these patterns are manifested in an emergence of unique rule-like preferences not observed in the baseline data, while the occurrence of tense markers with compositionally telic and atelic predicates largely reflects the distributional bias already present in the baseline data. In shifting the focus of attention in heritage language research from errors to overall patterns of language use, this study contributes to the existing work on grammatical restructuring in heritage language development and advances the view of heritage grammars as complex and dynamic systems.