The NRL has fined the Canterbury Bulldogs $20,000 for taking too long to run on to the field before this year's grand final.

The 83,000-plus crowd watched on the big screen as the Bulldogs got into a team huddle well after South Sydney had taken to the field.

The NRL said the runners-up remained in the dressing room for four minutes after they were told to run out.

"That kind of delay is unacceptable, particularly on such an important occasion like the grand final," head of football and former Canterbury chief executive Todd Greenberg said in an NRL statement.

The Rabbitohs started some ball-handling drills to keep warm, but were clearly unfazed, eventually running out 30-6 victors.

The Bulldogs have seven days to respond to the breach notice.