My company is too large (over 8,000 employees) to have an office party, but we do get an "Employee Appreciation" dinner every year served during lunch break. The choices are prime rib or turkey. No veg option. So, I'll be bringing my own marinated, grilled portabello mushroom, and I'll eat the steamed asparagus (I already asked, and it won't be prepared with butter) and plain baked potato (I'll bring my own Vegan sour cream and margarine) that comes on the side. Hopefully, the salad bar will also be open, but even if it isn't, I'll get enough to eat.
We also have a department Christmas pot luck party on-site, but it's always on Friday, and I work nights Sunday-Tuesday and every other Wednesday, so I'm not going to make a special trip out there (it's a 20 minute drive) just to attend.
On the other hand, my boss is giving each shift a pizza party to thank us for assisting with a big software rollout, and he came up to me and said, "I don't know what to get for you." I told him that I could do without, if it was going to be a pain in the rear, but if he wanted, he could either get me a veggie sandwich with no cheese and no mayo, or he could get me cheeseless veggie pizza. He said, "I didn't know there was any such thing as cheeseless pizza." LOL. But he was genuinely concerned and wanted to make sure I was included, which was very sweet. Of course, for the most part, I really like my job, so that makes things easy.
FWIW, if you didn't already have issues with your company (and you have my sympathy, since I've had similar problems with two former employers), I'd tell you to go ahead and go because Outback does have veg items (if you're creative), and since it's a party, you could call ahead and make special arrangements.