Where and when did the phrase "pop it in the oven" originate?
For 'pop', Oxford Dictionaries has:
Verb: [with object and adverbial of direction] put or move (something) somewhere quickly
She popped a pen into her pocket
In that sense, you could say that the phrase "pop it in the oven" is just a straight use of the verb rather than being idiomatic. (Though that doesn't explain how the word took on that meaning, or when this usage became popular)
The earliest usage Google Books have recorded is from 1869, from a book called Soimême:
I generally have one going, and I pop it in the oven the first thing and eat it hot, and I really want next to no breakfast.
That would make it nearly 150 years old at least.
On Google NGram viewer, it seems to come on in popularity in the 40s–70s and then rocketed in usage in the 80s — I'd wonder if this might have a corelation with the rise of cookbooks and TV shows by home cooks like Martha Stewart in the States and Delia Smith in the UK who were meant to be presenting cooking in a simple "no nonsense" approach (Disclaimer: complete conjucture!)