Temporal alignment of neural activity to rhythmic stimulation has been suggested to result from a resonating internal neural oscillator mechanism, but can also be explained by interval-based temporal prediction. Here, we investigate behavioral and brain responses in the post-stimulation period to compare an oscillatory versus an interval-based account. Hickok et al.'s (2015) behavioral paradigm yielded results that relate to a neural oscillatory entrainment mechanism. We adapted the paradigm to an event-related potential (ERP) suitable design: a periodic sequence was followed, in half of the trials, by near-threshold targets embedded in noise. The targets were played in various phases in relation to the preceding sequences' period. Participants had to detect whether targets were played or not, while their EEG was recorded. Both behavioral results and the P300 component of the ERP were only partially consistent with an oscillatory mechanism, but also only partially with an interval-based attentional gain mechanism. Instead, data obtained in the post-entrainment period can best be explained with a combination of both mechanisms.