Rice and beans
I think that proteins are made up of amino acids. There are several amino acids, but the only foods that have all of them are animal proteins, like meat, eggs, cheese, etc. If you're a vegetarian, you have to work a little harder to get them all. Eating a wide range of proteins such as beans/other legumes , soy products, nuts, rice, should give you everything you need. You don't have to have beans and rice at every meal, just keep a good variety going. If you're not a vegetarian, you will certainly get complete proteins without even trying!