He technically has two scenes, but the second one is right near the end, and consists mainly of him walking on screen and asking his son a question. He nails that scene, mind you, and I'm not being sarcastic, but it's the first scene, where he's drunk at about eight in the morning and driving his son to school, that made me say the first time I saw the film, and again last weekend when I saw the film for a second time, "Well shit. I had no idea."
I didn't know it was Timothy Bottoms. I am not, I admit, that familiar with his body of work. But I knew his name, and watching him in that first scene, seeing how quietly he plays shame and humiliation and guilt as his son (a very good John McFarland) is forced to take control of the situation, I realized that Timothy Bottoms is a freaking damn good actor. He gets all the torment and denial of the character across while also giving one of the most genuine drunk performances I've ever seen. Drunk acting must be one of the toughest things for any actor to do, and I say that as a non-actor who can only assume that's the case because I almost never see an actor playing drunk who doesn't botch it, or at least overdo it to the point where you can see his wheels turning. Bottoms gets it absolutely right. That, and everything else I've mentioned, in just a couple of minutes of screen time.
Check out the film, if you haven't already seen it, because the whole thing is quite good, but at least rent it for Bottoms. He does brilliant work here, and attention should be paid.