In a large bowl, combine oats, flour, sugar, cinnamon, baking powder, salt and vanilla and stir to mix well.
Add the margarine and cut it quickly into dry ingredients with two knives until the mixture resembles coarse meal and is no longer powdery. Do no overmix--bits of margarine will still be visible.
Set aside about half the oat mixture; press the rest firmly into the pan. Bake until lightly browned at the edges (but not fully baked), 13 to 15 minutes.
Meanwhile, mix the preserves with the spinach puree in a small bowl.
Spread blueberry mixture over the partially baked oat layer, then sprinkle with reserved oat mixture. Bake until topping is slightly browned, 20-25 minutes. Set the pan on a rack to cool completely before cutting into 12 bars.
Steam baby spinach(for mature spinach-remove stems) for about 30-40 seconds or cook in skillet with 1 tablespoons water for about 90 seconds or just until wilted. Puree in food processor or blender for about 2 min until smooth and creamy.