1. Preheat oven to 350°. In large bowl, combine all ingredients except bread. In shallow 1-1/2-quart casserole, spoon spinach mixture. Bake 20 minutes or until golden.
2. Meanwhile, cut bread slices into "tombstone" shapes. On cookie sheet, arrange in single layer. Bake 12 minutes or until crisp. On wire rack, cool completely. Decorate, If desired, with additional tinted Mayonnaise*.
3. To serve, arrange a few "tombstones" in cooked dip and serve with remaining "tombstones" and your favorite dippers.
TIP: In small resealable plastic bag, combine 1/2 cup Mayonnaise, 5 drops yellow food coloring and 1 drop red food coloring. Gently squeeze to mix. Snip one corner of bag and decorate "tombstones".