Sax is right about the "the concept of combining particular foods to obtain complete protein has been debunked."
Frances Moore-Lappé, in her book Diet For A Small Planet, originally proposed the idea of protein combining. That was in 1971* and based on 100-year-old studies. In her 1981 version of the same book she recanted and said that most plant-based diets require no special food combinations. This has got to be the most persistent nutrition myth ever.
Plants are almost all complete proteins.
However, then there is real life. All the whole Food plant-based diets suggest at least 3 servings of beans and at least three servings of grains**. And if you have 3 meals a day, then somewhere you are going to have a meal that combines grains and beans.
I was never a big fan of Beans and Rice. Until I went to a new Cuban restaurant and had their Cuban Black Beans and Rice.
Now its become one of my favorite meals. I make a big pot of Cuban Black Beans on the stove. *** I then separate it into one cup portions and freeze most of them. Just keep one cup in the frig and add it to one cup rice for a super quick and nutritious lunch.
I also like to do the same thing with regular black beans to add to salads. When I add it to salads I add just 2 - 3 tbsp.
According to Gregar,
A serving =
1⁄4 cup hummus or bean dip
or 1⁄2 cup cooked beans, split peas, lentils, edamame, tofu, or tempeh
or 1 cup fresh peas or sprouted lentils
* I still have my copy
** this may be where there is the most divergence among the big WFPB diet gurus. Fuhrman suggests only one serving of grains a day if you are trying to lose weight. Gregar recommends 3. and I think McDougall doesn't set any limits.
***my crock pot is sort of small so I can only make two servings of it at a time - but it requires less attention - so i'm not sure which I prefer - maybe another good reason to get that Instant Pot I have been dreaming about,