Baking Substitute oil for butter

Yes long before Crisco, butter , oleo , other vegetable oils , people used lard. It still works , its cheap, and bake a lot because of the size.

Earth Balance is great for baking, although one must use the stick form rather than the one that comes in a tub. However, if you don't want the added salt in EB, coconut oil is a good substitute. It's not a 1:1 ratio, though, as butter is not 100% fat; see https://www.thekitchn.com/how-do-i-substitute-coconut-oil-for-butter-good-questions-195494

Ellie -
Good to work from recipe that already has been baked with oil and found good, like the one SillyBee sent.
However, when converting recipes that start with butter to oil, I use only 80% volume of oil, to reflect that butter sold in USA averages about 4/5 fat and 1/5 water (there are minute amounts of milk solids in the 1/5 part).
If needed, I add some liquid (compatible with the other ingredients) to compensate for the lost 1/5 volume liquid.

Gosh I hope someone knows the answer to this. Baking is a tricky creature, very much chemistry based, so changing ingredients like sugar can alter the final result. That being said, my chocolate chip recipe from ATK uses melted butter. So it's *possible* oil could work. If you give it a try with oil and the cookie spreads too much, try using less next time and chill the dough before baking. Good luck. Tell us how it turns out.