If you're a vegetarian or a vegan, you have a lot of power over restaurant menus. A recent survey found that to attract millennials, a restaurant must offer options for both vegetarians and vegans, according to the Portland Press Herald.

Not all millennials are non-meat eaters, but the survey found that 45 percent of them choose to follow a vegetarian or vegan diet, even if it's only some of the time. If one of those in the 45 percent can't find anything appealing on the menu when a group dines out together, that person gets the veto vote. And those looking for meatless options aren't satisfied if salads and portobello burgers are their only options.

To welcome all eaters, restaurants are becoming more vegetarian- and vegan-friendly. Even fast-food chains like White Castle are adding vegetarian sliders, and new fast-food restaurants like the organic Amy's Drive Thru in California have plenty of vegetarian and vegan offerings. (In fact, every Amy's menu item can be made vegan.)

There's a handy online tool for finding the veg-friendly restaurants in any region. Happy Cow allows diners to search for veg-friendly dining options within a certain mile radius of a ZIP code. If you check the "veg-friendly" box, you'll get a list of restaurants that cater to all eaters. A short description of each restaurant's offerings is included, and diners can rate and review the restaurant on the website.

From the reviews, you'll see that a restaurant with many meat dishes may also offer a "Mock Duck Sandwich with a mouth-watering Peanut Butter BBQ sauce that's supposed to be like a pulled-pork sandwich and is served with a side of tasty sweet potato fries." That's definitely more appealing than the once-ubiquitous portobello burger that most restaurants threw on their menu to satisfy vegetarians.

Interestingly, restaurant menus are not the only thing millennials are influencing. They're also having an impact on restaurant design. Along with meat-free dishes, they also want things like communal and movable tables and plenty of outlets to recharge their mobile devices. As millennials come into their "peak spending years," expect to see more of these changes as restaurants and other businesses give them what they want.

Robin Shreeves ( @rshreeves ) focuses on food from a family perspective from her home base in New Jersey.