In one aspect, a method includes (i) accessing broadcast-schedule data associated with a channel; (ii) using the accessed broadcast-schedule data to identify an upcoming content-modification opportunity on the channel; (iii) responsive to identifying the upcoming content-modification opportunity on the channel, identifying a content-presentation device tuned to the channel; and (iv) causing supplemental content to be transmitted to the identified content-presentation device, to facilitate the identified content-presentation device performing a content-modification operation related to the identified upcoming content-modification opportunity on the channel.