West Brom midfielder Dorrans and Blackpool's Adam are both key men in their respective teams.
Moyes said: "Are there enough Scots who are able to perform in the Premiership? That's the biggest question and I believe the answer is no.
"The English Premier League is so multicultural and worldwide that it's hard to get in that league as there are players from all over the world trying to.
"They've shown Scottish lads can come down to England and succeed. We have a load of boys who are showing that at present."