Heritage receptive bilinguals (RBs) are individuals who report understanding but not speaking their family language. This study tests whether semantic features of functional morphemes, namely tense, aspect, and agreement markers, are accessible to them in comprehension. RBs in this study are fluent speakers of English with receptive knowledge of Labrador Inuttitut. Many RBs showed fluent-like comprehension of aspectual suffixes, subject-object-verb agreement suffixes, and past versus future contrasts in tense suffixes, but most could not identify remoteness degrees in tense suffixes. Lowest-proficiency RBs did not show knowledge of any morphemes. Remoteness features are missing from most RBs’ grammars; the same applies to many features in LRBs’ grammars. Some RBs showed inconsistent performance: better than chance, but worse than fluent speakers. The corresponding parts of RBs’ grammars are therefore fluent-like, but access to them is difficult. RBs’ grammars consist of fluent-like parts, parts with reduced access, and incomplete parts.