Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add leek and next 4 ingredients (leek through garlic), and sauté 5 minutes. Add artichokes and bell pepper, and sauté 3 minutes. Stir in beans, and remove from heat.
Melt butter in a medium saucepan over medium heat. Add flour, and cook 2 minutes, stirring constantly with a whisk. Gradually add milk, stirring with a whisk until blended, and cook until slightly thick (about 4 minutes). Remove from heat. Add feta and 2 tablespoons Parmesan; stir until cheese melts.
Spread 1/4 cup cheese sauce in bottom of an 8-inch square baking dish coated with cooking spray. Arrange 2 noodles over cheese sauce; top with half of leek mixture, half of spinach, 1/4 cup mozzarella, and 1/2 cup cheese sauce. Repeat layers, ending with noodles. Pour remaining cheese sauce over noodles, and sprinkle with 1/4 cup mozzarella and 1 tablespoon Parmesan.
Cover and bake at 375° for 35 minutes. Uncover and bake 15 minutes or until top is golden. Let stand 5 minutes.