Use serrated knife to cut V-shaped piece from top of bread loaf, cutting to within 1/2 inch from bottom of loaf. Remove inside of bread loaf, leaving 1/2-inch-thick shell. Place bread shell on parchment-covered baking sheet. Reserve removed bread and top of loaf for another use.
Heat oil in large saucepan on medium heat. Add spinach; cook 2 to 3 min. or just until wilted, stirring frequently. Remove from heat.
Whisk eggs in medium bowl until blended. Add remaining ingredients; mix well. Stir in spinach. Spoon into bread shell.
Bake 40 to 45 min. or until filling is puffed and set in center. Cool 5 min. before cutting into 6 wedges.