In a 2-quart pot, bring water, oregano, and salt to a boil. Turn off heat and immediately add the couscous. Level the couscous with a fork to make an even layer, cover with a lid and let steam for 5-7 minutes. Remove lid, fluff couscous with a fork. Let cool completely before adding the vegetables.
While the couscous is cooling, prepare the remaining ingredients.
Combine 1 teaspoon lemon juice with the avocado separately before adding to the bowl of vegetables.
Add couscous to bowl.
Pour EVOO and remaining lemon juice over all the ingredients, stir well to combine. Season with salt to taste.
If the couscous isn't breaking apart evenly and you notice some clumps, drizzle a teaspoonful of EVOO in the couscous and use your fingers to break the clumps apart. You can also fluff the couscous over a large plate or shallow bowl.
This couscous salad can be made a day in advance. Keep it refrigerated until the day of the party/dinner. Keep it covered, but take it out about an hour before you start serving so it's not too cold.