Heat the oven to 325°F (165°C). Lightly grease a 9-inch pie or quiche pan and set it aside.
Place the thawed spinach in a small saucepan over medium heat and warm until fully softened. Transfer to a sieve or clean towel and press firmly to remove excess moisture.
In a large bowl combine the drained spinach, chopped green onions (white parts), beaten eggs, cottage cheese, and shredded Cheddar. Stir until the mixture is evenly blended.
Pour the mixture into the prepared pan and smooth the surface with a spatula so it cooks evenly.
Bake uncovered for 45 minutes, then remove from the oven and evenly sprinkle the crushed croutons over the top.
Return the quiche to the oven and bake 15 more minutes, or until the filling is set and the center is firm when gently nudged.
Let the quiche rest for a few minutes to firm up, then slice and serve warm or at room temperature.