In a medium stockpot, cook the quinoa following the instructions on the bag.
In the meantime, while quinoa is cooking, in a large bowl, combine the cucumber, tomato, red onion, and red wine vinegar. Gently toss them around to coat in the vinegar. It'll look like too much vinegar but don't forget that you have the quinoa to add in :) season with salt and pepper to taste.
When quinoa is ready, add to the bowl and gently mix around until everything is well combined. If you like your salad more vinegary add more to taste.
Pop quinoa salad in the fridge for 30 minutes to cool.