Presumably the reason you're cooking directly on the oven rack is to let the fat drip down.
If so, do yourself a favour and get yourself a roasting rack .
It's an inexpensive piece of equipment that you place in a baking pan or on a cookie sheet; the food cooks on the rack and the pan/sheet catches all the drippings.
Way better than trying to replace an entire oven rack.
And if you really hate cleanup, you can line the pan with parchment paper or aluminum foil and just throw the rack in the dishwasher when you're done.
cooking.stackexchange.com/users/41/Aaronut
I would suggest that the answer is that it isn't common.
I would normally use sheet pans/trays and a rack on top of that.
It's much easier to put food in and out of the oven that way.
cooking.stackexchange.com/users/231/talon8
If you want to continue to cook on the racks in this way there is no need to ever replace them.
When mine get really dirty
I use this oven cleaner you just put the racks in a bag with the cleaner and the next morning they look brand new.
It's probably horrible for the environment but can't be worse than producing new racks just beacuse mine are dirty.
cooking.stackexchange.com/users/2391/vwiggins
I roast directly on rack as well using the broiler, mostly poultry(thanksgiving turkey on the rack divine).
I put the bird(breast side down)
as close as possible to the upper heating element(my broiler is the top of the electric oven), and i set the temp to 320 or so, then set the drip pan on the bottom rack, as far down as it will go.
I check back every 30 mins or so to make sure that that there arent any areas that are burning.
I flip the bird right side up at about 1 hour just to brown the skin on the breast side a bit.
Once the bird is done(at your own discretion), i let it rest for 20-30.
I dont like the idea of putting a pan directly underneath an extra rack, because in my mind, the pan limits the flow of heat to what you are baking, and still creates a humid environment directly blow that that limits the development of a crispy skin.
The cleaning aspect kinda sucks, but some oven cleaner a hot rack along with some patience is all your need
Personally, i dont clean the rack every time i roast on it, unless i plan to use a pan, or have used a pan on the rack.
cooking.stackexchange.com/users/None/
Before I got a pizza stone I'd put store bought pizzas straight onto the rack as it gave a better crust.
The only reason I can think of doing it is basically laziness - I'd do it with cheese on toast if the grill pan was too dirty to use.
I'd also sometimes do baked potatoes without a tray as Id cover them with tin foil.
cooking.stackexchange.com/users/2010/NBenatar
I would simply purchase a wire rack for cooling cookies (not coated) and place it on top of a cookie sheet.
Alternatively, place it across a glass Lasagna pan for more air flow underneath and better drip catching.
cooking.stackexchange.com/users/1148/Chris Cudmore
I dont know if it's common, but I use my racks to grill pork chops and steak.
I don't like the grilling outside taste
so this works for me!
cooking.stackexchange.com/users/27559/Jodie
A leg of lamb slow cooked directly on the rack is delicious and l would never cook lanb in a pan again.
Line the pan underneath with foil and the clean up is easy.
cooking.stackexchange.com/users/50401/Maureen
I have never heard of this until 5 minutes ago when I found a recipe for it.
I don't thinkit's common and I've never done this but am considering doing it with an 8 lb bone in ribeye roast because I saw a recipe for it to be placed directly on the rack.
Someone said it was lazy and many of you said to use a roasting pan, but you're missing the point: airflow.
When you use a pan, you restrict airflow
and when you combine a pan with a rack, you're still limiting airflow.
I t sounds like a brilliant idea If you want your meat crispy or crusty all over.
I don't see why you'd have to replace your oven racks, just take them out and wash them.
If you put a pan underneath,that should catch the fat.
I have a roasting rack
but I'm going to try this for Christmas tomorrow.
I suspect my dinner guests will find it odd
but I'm keeping fingers
crossed dinner willBe
so delicious they'll overlook the cooking method
cooking.stackexchange.com/users/71594/Carolyn
Is it common to cook food directly on the oven racks?  I often do this (with a container for drippings) and was wondering if this is common or if there is a better solution.  It has worked out fine for me, but sometimes replacing these racks can be costly.  I do not replace them often, and they are not very hard to clean, but I would like to get some ideas on if I am doing this wrong.
Cooking food directly on oven rack
cooking.stackexchange.com
<equipment><oven>
cooking.stackexchange.com/questions/10431
cooking.stackexchange.com/users/3760/Naomi Campbell
A roasting rack over a sheet pan/tray would be a better way to do this. Use a roasting rack with a tray built in.
It would be easier to roast on a rack with a special tray underneath for easier clean up.