Abstract: A system and method automatically transforms preexisting advertising creatives adapted for a first content service environment into advertising creatives for a second content service environment. The transformed advertising creative are then suitable for initiating a new advertising campaign. In one example, the system transforms advertising creatives from search advertisements and display advertisements into creatives for a stream advertising campaign. Stream advertisements may then be placed into a stream of content displayed on a user device. The transformed advertising creatives may be included in a proposal to a prospective advertiser. The advertiser then can choose to accept the proposal. The process of creating new advertising creatives for the proposal to the advertiser is simplified, automated and made more efficient.