Mediterranean Spinach Strata

Preheat oven to 350 °. Place bread slices in a single layer on a baking sheet. Bake at 350 ° for 12 minutes or until lightly browned. Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add onion, garlic, and mushrooms; sauté 5 minutes or until tender. Sprinkle flour over mushroom mixture; cook 1 minute, stirring constantly. Add 1 bag of spinach; cook 3 minutes or until spinach wilts. Add remaining spinach; cook 3 minutes or until spinach wilts. Stir in 1/4 teaspoon salt and 1/4 teaspoon pepper. Place half of bread slices in bottom of a 13 x 9-inch baking dish coated with cooking spray. Spread spinach mixture over bread. Top with tomato slices; sprinkle evenly with feta and half of Asiago cheese. Arrange remaining bread slices over cheese. Combine 1/4 teaspoon salt, 1/4 teaspoon pepper, milk, and remaining ingredients, stirring well with a whisk. Pour over bread; sprinkle with remaining Asiago cheese. Cover and chill 8 hours or overnight. Preheat oven to 350 °. Uncover strata; bake at 350 ° for 40 minutes or until lightly browned and set. Serve warm.