Heat 2 tablespoons of the oil in a large nonstick skillet over medium-high heat.

Add garlic and onion, and cook until just beginning to soften, about 2 minutes.

Add potatoes, salt and pepper, stir well, cover and cook, stirring occasionally, until potatoes are just tender, about 15 minutes.

Transfer to a large bowl, add spinach to the bowl and toss to combine.

Let cool 10 minutes.

Wipe the skillet clean.

Stir peppers and eggs into potato mixture.

Heat another 1 1/2 teaspoons of the oil over medium heat.

Transfer potato mixture to the skillet and cook, running a spatula around the edges and gently shaking occasionally to prevent sticking, until eggs are set and bottom is golden brown, 12 to 14 minutes.

Carefully invert onto a large plate.

Heat remaining oil in the skillet and slide tortilla back in, cooked side up.

Cook about 5 minutes or until golden brown.

Transfer tortilla back to the plate and let cool at least 10 minutes.

Slice into wedges and serve.