First-half goals from Robert Snodgrass and leading scorer Jermaine Beckford put Leeds in control and Neil Kilkenny's last-minute strike put the seal on another comfortable victory for Grayson's men.
He said: "We've set ourselves up to have a successful season but you don't get promotion at the end of November and we're there to be shot at.
"It was a really difficult game for us and a potential banana skin but, putting everything together, we produced our best performance of the season."
United have only lost one of their last 16 league games, and they have scored 16 goals in their winning five-match run, but Grayson is taking nothing for granted.
He added: "We set ourselves high standards, are very committed and we must keep at it.
"I'm happy with our points tally but we are determined to be level-headed. We have a fantastic work ethic and this must be maintained as we look to keep our position at the top of the table."