I believe it was the show in 50s "I love Lucy". She was white and he was Cuban.
November 22, 1968 in the Star Trek episode "Plato's Stepchildren".
young and the restless
I am assuming you are talking about American Caucasians and African Americans. There is no answer to this question. As far back as the good old plantation days there was serious romantic affairs going on, but well hidden.
Happy days
No. They may have been the first "multiracial" couple on television, if you accept that "of Spanish descent" is a different "race" than "white".
Fred and Velma (or Welma) Flintstone.
the Munsters.
Pat Sajak and Vanna White have been the only hosts for the current Nighttime Show. They were also on the daytime show where Chuck Woolery was the first host to have have the TV series
St Elsewhere
Mary Kay and Johnny were the first couple to appear in bed together in a prime time television show, it was actually the fist sitcom on television in 1947. http://www.snopes.com/radiotv/tv/marykay.asp
Gayle King received her first Daytime Emmy Award in 2016 for Outstanding Informative Talk Show for "CBS This Morning." She was also nominated multiple times throughout her career, but this win marked a significant recognition of her work in daytime television.
Eureka is partially good but lacks the depth after the first couple episodes. Even so it can humor you for a couple of seasons but nothing great about it.