Ray Charles and Chuck Berry made it popular, if not to the same extent as what The Beatles did.
Well, if we're gonna assume that Ray Charles, Chuck Berry, and maybe a few others were the ones that started the trend of bands/artists writing and performing their own material, who are the other name brand acts that bridged the gap between the earliest rock and roll guys writing their own material, and the Beatles and Beach Boys, starting in '62 or whatever?
I wasn't around when it was happening and I'm no expert, but when both the Beatles and the Beach Boys hit the scene it was still pretty uncommon for pop/rock acts to be writing their own material - that's something that they've always been credited for. After they started dominating the charts, it became the norm and has continued to be that way ever since. There were lots of big pop stars between when Chuck Berry hit the scene and when the Beatles hit the scene and yet the Beatles (along with the Beach Boys) are credited with starting the trend.