Rinse quinoa well in a wire strainer to remove bitter oil.
In medium sauce pan, bring water and quinoa to a boil, then reduce heat to low, simmer 10-12 minutes or until quinoa is tender and most of water is absorbed. Transfer quinoa to a bowl and let cool completely.
Chop and slice all vegetables and add to cooled quinoa.
In a small bowl, whisk lemon juice, olive oil, garlic, salt, and cayenne pepper (if used) together. (Can also shake in a jar if not using a whisk.) Pour over quinoa and veggies and mix gently.