Barnes has written several episodes of "The Outer Limits" and "Baywatch". His "A Stitch In Time" episode of The Outer Limits won an Emmy Award. He has also written the episode "Brief Candle" for "Stargate SG-1" and the "Andromeda" episode "The Sum of Its Parts". Barnes's first published piece of fiction, the 1979 novelette "The Locusts", was written with Larry Niven, and was a Hugo Award nominee. Barnes subsequently collaborated with Niven on several other books, including two books with both Niven and Jerry Pournelle. Barnes said he clashed politically with the two conservative writers but enjoyed working with them, calling it "a tremendous learning opportunity".