Steinberg was born in Los Angeles and stood just 3'1" tall. His adoptive parents also suffered from dwarfism. Steinberg was raised in Queens, New York, where he excelled in comedy in school as a way to overcome shyness over his short stature.
He first began acting on stage while studying at Messiah College in Pennsylvania. He switched to professional theater after college. His theater credits included performances notable theater companies including the Guthrie Theater in Minneapolis, the Center Stage in Baltimore and the New York Shakespeare Festival. He also starred in a Grammy-nominated national touring production of The Wizard of Oz and Baz Luhrman's production of La Boheme in Los Angeles and New York City.
While Steinberg was best known as Meegosh in Willow, his other film credits included roles in The Hebrew Hammer and Love & Sex. His television appearances included a guest spot on the 2007 Ugly Betty episode, Giving Up the Ghost, as well as roles on Zoey 101, Charmed, The Equalizer, Are You Afraid of the Dark? and The Days and Nights of Molly Dodd.