I've toasted oak in my gas grill. wrapped a package of oak sticks in foil, poked a few holes for smoke to escape and fired it up. some turned into charcoal but most toasted nicely. I kept the grill at around 300 degrees and when the package would start smoking, removed it from the heat. if it was not toasted enough, I just put it back on.
I probably will not toast anymore. It is easier for me to just buy my oak cubes, chips or staves.