Preheat oven to 400°F Spray a 9" springform pan with non-stick cooking spray; sprinkle with 2 tablespoons of bread crumbs.
In a large nonstick skillet, heat oil. Add onions, cook and stir until softened (about 5 min). Stir in chard & garlic, cook and stir about 5 min, or until chard is tender.
Meanwhile, combine ricotta, eggs, salt, pepper and remaining 2 tablespoons of bread crumbs in a medium bowl. Stir in the chard mixture. Spoon into the prepared pan. Bake until puffed, golden, and firm to the touch (about 45-50 minutes). Let stand for 10 minutes before serving. Cut into 4 wedges.