In a small, nonstick omelette pan (really, small!), coat the bottom with olive oil and place on burner at a medium-high heat. I use a generous amount of oil to help the eggs brown (and because I like the flavor), but you can go lighter if you'd like.
When oil is hot, remove pan from heat and add onions and garlic. Allow to saute for a minute or so, stirring as needed. Meanwhile, turn the burner down to medium.
Crack 2 eggs over the sauted onion and garlic, using a spatula to distribute the veggies throughout the egg whites before they start to turn white. (This needs to be done relatively quickly.)
Quickly add the feta and olives into the uncooked eggs, avoiding breaking the yolks.
Add salt and pepper now, if desired.
Cover pan with a clear lid and return to the heat. The clear cover will help the top of the eggs cook and you'll be able to gauge their progress without picking up the lid and losing the steam.
Cook to desired doneness, or until yolks have formed a white film over them. I cooked mine for about 2-3 minutes, tops, and they were done perfectly (yolks mostly runny but partly done on the bottom).
Remove from heat and garnish generously with cubed avocado over the top of the whole dish.
Serve immediately, in the pan. (I guess you could try to remove it, but I like eating from the pan as it keeps the eggs warm throughout the meal.).