Clean spinach, remove stems, and coarsely chop the leaves. Heat Greek dressing in a very large skillet, add chopped spinach, and cook over medium heat, stirring often, until wilted. Raise heat to high and cook until nearly all the liquid as evaporated. Turn off heat and stir in black olives. Keep warm.

Make omelets one at a time in a small, non-stick (8-inch) skillet with sloping sides.

For each omelet, beat two or three eggs in a bowl. Heat a little olive oil over high heat in the skillet. Pour in eggs; they will immediately begin to set on the bottom. With a spatula, pull egg from outer edges of pan towards the center; the uncooked egg will spread and cook. Keep doing this until most of the egg is set - this will only take a moment - then spread any remaining uncooked egg across surface of omelet. Reduce heat to low.

The egg will continue to cook as you distribute some of the crumbled feta, spinach filling and pepper over the surface. Holding a plate close to the pan with one hand and shaking the pan slightly with your other hand, slip omelet onto a plate, rolling it into either a cigar shape or folding it over into a half-moon.

Serve immediately or keep warm in a 200-degree oven while you prepare additional omelets.