While writing an answer to Was there any reason to think that there might be students younger than 17 coming for the Triwizard Tournament?, I came across this line:
“A Portkey?” Ron suggested. “Or they could Apparate — maybe you’re allowed to do it under seventeen wherever they come from?”
"You can't Apparate inside the Hogwarts grounds, how often do I have to tell you?" said Hermione impatiently.
Harry Potter and the Goblet of Fire, chapter 15: "Beauxbatons and Durmstrang"
Hermione adds the "how often do I have to tell you" as if she's told him many times before. So, to help substantiate my answer a bit, I decided to look for exactly how many times she's told him that Apparation doesn't work in the Hogwarts grounds. However, I was only able to find one instance where she tells him this, and only one other time it's mentioned before this.
Hermione tells Harry and Ron in The Prisoner of Azkaban:
“Maybe he knows how to Apparate,” said a Ravenclaw a few feet away, “Just appear out of thin air, you know.”
“Disguised himself, probably,” said a Hufflepuff fifth year.
“He could’ve flown in,” suggested Dean Thomas.
“Honestly, am I the only person who’s ever bothered to read Hogwarts, A History?” said Hermione crossly to Harry and Ron.
“Probably,” said Ron. “Why?”
“Because the castle’s protected by more than walls, you know,” said Hermione. “There are all sorts of enchantments on it, to stop people entering by stealth. You can’t just Apparate in here. And I’d like to see the disguise that could fool those Dementors. They’re guarding every single entrance to the grounds. They’d have seen him fly in too. And Filch knows all the secret passages, they’ll have them covered…”
Harry Potter and the Prisoner of Azkaban, chapter 9: "Grim Defeat"
The only other time it's mentioned before this incident in GoF is when Ron is unconscious, later in PoA:
“He must have Disapparated, Severus. We should have left somebody in the room with him. When this gets out —”
“HE DIDN’T DISAPPARATE!” Snape roared, now very close at hand. “YOU CAN’T APPARATE OR DISAPPARATE INSIDE THIS CASTLE! THIS — HAS — SOMETHING — TO — DO — WITH — POTTER!”
“Severus — be reasonable — Harry has been locked up —”
Harry Potter and the Prisoner of Azkaban, chapter 22: "Owl Post Again"
So why does Hermione seem so exasperated here? She's only told him once before. Why the "how often do I have to tell you"?