Methods and apparatus to measure audience composition and recruit audience measurement panelists are disclosed. An example media device disclosed herein includes means for analyzing a video stream of media being presented by the media device, the means for analyzing to detect a first code embedded in the video stream, the first code referencing first audience measurement data to identify the media. The method further includes means for modifying a media output to: after detection of the first code, provide a request for an audience member to join an audience measurement panel; and, after receipt of a response to the request, cause the media device to present a second code, the second code including information that, when the second code is scanned with a portable device other than the media device, is to direct the portable device to a website to provide additional audience measurement data.