http://www.the-waltons.com/season1.html#The_Love_Story

It appears to have been written by Jerry Goldsmith
THE LOVE STORY (18 Jan 1973)
Writer: Earl Hamner
Director: Lee Philips
Music: Jerry Goldsmith

http://us.imdb.com/Credits?0068149

Other music credits for the first season are given to:
Alexander Courage (some episodes)
Jerry Goldsmith (theme) (some episodes)
Arthur Morton (I) (some episodes)

Sincerely,
Gargoyle