Foster was a major contributor to the 1979 Earth, Wind and Fire album I Am, both as a studio player and arranger, as well as being a cowriter on six of the album's tracks.
Foster merupakan kontributor utama 1979 Earth, Wind and Fire album I Am, keduanya berperan sebagai pemain dan aranger studio, selain juga ikut menuliskan enam lagu dalam album tersebut.