Preheated Oven

[ll_billym]

Why on frozen food does it say "place in an oven preheated to xxxx"?

 

I'm sure there is a reason but surely the food would be ready to eat faster if you just put the food in when you turn the oven on, then it would be cooking (not very quickly though) while oven comes up to the set temperature.

[Tweed]

Some foods require that you cook them quickly. Pastries for example.

[Clanad]

The rest of your quoted phrase would include instructions on how long, in time, the dish should remain in the oven to cook appropriately.  This can only be accurately predicted when the oven is already at the correct temperature.  Most ovens reach a given temperature in differing times and, therefore, could not be counted on to heat the food in a predictable time...

[Englishbird]

i'll admit to putting things in straight away and just adding 5 mins onto cooking time! but then i'm very lazy.