If you're a vegetarian or vegan, this might be disconcerting, but it doesn't necessarily have to be a deal-breaker. (Note: I am going to assume you are the vegetarian, but if it's the other way around read on. You might gain a better understanding of your mate's choices and learn some ways to make mealtime more palatable for both of you.)
WHY, WHY, WHY?
There are a lot of reasons people choose vegetarianism. Sometimes it's as simple as disliking the taste of meat or believing a vegetarian diet is healthier. You might also be morally opposed to eating meat and animal products, or feel it's better for the environment to stick to plants.
Either way, it's important to explain your reasons to him in a non-judgmental way, and preferably not during mealtime. No matter how disgusted you might be by the sight of a hunk of rare filet mignon, your partner will be much more receptive to your message if you avoid turning his stomach while it's growling.
Of course it's possible he'll decide to chuck the burgers and join you. But remember: just as he can't force you to eat meat, you can't force him to switch to shoots and stalks.
MEALTIME IS GET REAL TIME
Once you can work through the "meatier" issues, then mealtime conflicts can be resolved rather quickly with a little flexibility and creativity on both your parts.
Cook your own: Make your own delicious vegetarian dishes and encourage him to try them. It could be that he enjoys your creations so much he doesn't miss the meat.
Go out on the town: Find some local restaurants that offer menus with both vegetarian and meat-based options. You may also choose to stay vegetarian at home, and let him chow down on carnitas during his lunch break.
Serve up a side: Vegetarian meals can make great side dishes. Leave the grilling to him, while you cook up the accompaniment (a lot for you, a little for him). Alternatively, if he's doing steak and potatoes, load up on the potatoes as a main dish and steam up some veggies to round things out.
Substitute something: From veggie burgers to fake bacon, there is a wide variety of substitute meat products available in stores now. Not all of them are appetizing for meat eaters, but you'll never know until you try.
Humor me: Whatever you're serving up, mix a little humor in with it. Have a blind taste test that mixes up real meat with substitutes. Maybe you'll find one he actually likes! And the blindfold could lead to other fun bonding activities…
RECIPE FOR HARMONY
Many people are in relationships with people of opposing viewpoints. That's what keeps life interesting. But what keeps you together is the ability to focus on your similarities more than you do on your differences.