The nation's largest phone companies sell packages of wireless phone service, Internet access and pay TV to consumers. Now they're taking integration one step further, airing video programming and selling ads across all three platforms.

Content and advertising deals used to be struck separately for each platform. But Verizon Communications Inc. and AT&T Inc., for instance, have cut deals with media companies that allow them to distribute programming from "Saturday Night Live" clips to user-generated video to cellphone, broadband and TV customers. Recently, the phone companies have begun to sell ads across all three screens. They're ...