As a disclaimer, you probably shouldn't put flammable material like wood inside an oven and leave it unattended, and you should also look up the flashpoint or autoignition temperature of whatever you're working with. I have used a 300 degree oven to dry black walnut, sitka spruce, red cedar, padauk, mango, goncalo alves and eastern hard maple without any problems.
Nevertheless, don't burn down your house and then say I told you it was safe to do so!