Preheat the oven to 400 degrees F.
Lay the bacon in a saute pan and bake for 15 minutes, until crispy. Transfer the bacon to a plate lined with paper towels and let it drain for a couple of minutes.
Scoop out each half of the avocado using an oversized spoon and arrange on a platter. Scatter the watercress over the avocado and crumble the bacon over the top. Drizzle with the lemon juice and olive oil and sprinkle with salt and pepper.