Oh great TexAgs,
Attic access is in the garage. The house has two attic fans on thermostats and extensive venting cut into the eaves for airflow. Insulation was blown in recently. The garage still gains a lot of heat, despite being on the east side and having fairly decent shade. I've propped open the attic door slightly to see if I could draw some heat out of there when the attic fans kick on. I don't notice much difference, so maybe there's no point fooling around with this, but I can't leave the attic propped open very far due to the parking/house entry set-up.

Is there much to be gained by cutting a vent hole in the attic access door and installing a vent cover? I have an extra vent cover laying around but don't know if there's any point in messing with the project if it won't help cool the garage. Thoughts?

Possibly. But you have to get inlet air into the garage somewhere - leave the door up a couple inches, or install a vent in the wall. I too leave me access door open a little in the garage and will leave the door up a few inches when really hot.

Keep in mind this does break certain firebreak standards letting fire easily and quickly get up into the attic and spread from the garage and could theoretically let fumes or bad gases from the garage get over to the living area.

If you know you are aggressively venting the attic the gas concern is pretty small, but the fire one is still there.

Absolute is right on about the make-up air. Venting your attic stairs provides no tangible benefit unless you have an exhaust/make-up air system active in your garage.

As to the fire issue, I understand that Absolute is quoting the intent of fire code. The reality, however, is that your standard attic access door has no fire rating and only minimal draft-stop properties because the access door isn't sealed.

If there's a fire in your garage, you're only talking about a difference of seconds, whether the attic door is opened or closed, before fire reaches the attic. And since it's not sealed, the negative pressure from your exhaust fans in the attic, will suck the smoke into the attic in an instant.

Like Absolute said, fumes should not be an issue. The inside of your house is under positive pressure, and the attic is under negative pressure, so what little fumes may exist will be exhausted through your roof.

In short, adding garage door insulation and some type of radiant barrier to your roof are the only real ways to solve your problem. Also, if you have one or more garage walls that are not immediately adjacent to living space, chance are they are not insulated.

Very solid input, all the way around. Thanks peeps.