Baking corn on the cob fully takes around 25 to 30 minutes depending on how well baked you like the corn on the cob.
I like my corn on the cob baked for 30 minutes which cooks it enough to make it good to eat.
What I do is preheat the oven and then place the corn into the oven with the husks on directly onto the oven rack and then let the corn on the cob bake for 30 minutes.
Then after 30 minutes turn the oven off and then remove the corn on the cob from the oven and peel the husks.
Then add your butter or whatever you want to add to the corn on the cob and then after they cool down you can enjoy it.
You can place the corn on the cob in foil in a baking sheet if you want too however I find just cooking the corn on the cob in the oven with the corn husks on them works just fine.