My sister and I used to watch this movie when we were little (1980's) that had a green dragon who ate these things that looked like white onions. I remember a very specific scene where he is in a cave eating the 'onions.'... any ideas? It's driving me crazy!

Possibly "The Flight of Dragons"

The Flight of Dragons (1982)

Pete's dragon?

No it wasn't flight of the dragon or pete's dragon or puff the magic dragon... those were all good though.

I'm afraid this may have a been one of those rare pbs special kind of movies. I think the dragon may have been some sort of an outcast in the movie... maybe? Thanks for your suggestions!