1. Preheat oven to 350°.
2. Arrange bread cubes in a single layer on a large baking sheet or jelly-roll pan. Bake at 350° for 18 minutes or until golden. Cool slightly.
3. Heat a large nonstick skillet over medium-high heat. Add olive oil to pan; swirl to coat. Add leek and next 5 ingredients (through garlic); sauté 10 minutes or until leek begins to brown, stirring occasionally. Stir in mushrooms; sauté 8 minutes or until mushrooms are tender, stirring occasionally. Place the mushroom mixture in a large bowl. Add toasted bread cubes, chicken stock, and remaining ingredients except cooking spray. Toss mixture gently to combine. Spoon the mixture into an 11 x 7inch glass or ceramic baking dish coated with cooking spray. Bake at 350° for 45 minutes or until top of stuffing is browned.