I found this sentence in a textbook. It's
I cooked the fish slowly on / under the grill.
According to the author, the correct answer is under.
I also used Google. It turns out that there is more under the grill than on the grill. When I think of the word grill, the next picture comes to my mind.
How can we cook the fish under the grill when the food is actually on the grill?
Best Answer
There is a usage difference between British and American English. Although a grill is everywhere a frame of metal bars used for cooking on a flame, Americans draw a distinction between grilling (cooking over a flame) and broiling (cooking under a flame), as when you use the broiler in your oven:
As quoted in this LanguageHat post,
There are many differences in food-related terminology, some noted on our sister site, Seasoned Advice, in Translating cooking terms between US / UK / AU / CA / NZ.