Carin came up with this and it has become a go-to recipe for us. It's super quick-and-easy to make, goes with almost anything (and is great on its own), is nicely filling, and is tasty! The kidney beans are a really nice touch -- they add a little sweet to the dish makes everything come together well.
Put the olive oil and vinegar in a bowl. Season generously with salt and pepper. Whisk together until well-blended. Add beans, cucumber, parsley, and tomatoes. Toss until well-coated. Serve.
Note: This actually keeps well in the refrigerator and the dressing continues to season the ingredients -- I think it just gets better with age.