Heat 2/3 cup water to boiling. Add 7-grain cereal to a heat-safe bowl. Carefully pour boiling water over cereal; stir to combine. Cover; allow to set for 12 to 24 hours on counter.
In stand mixer fitted with paddle attachment, add 1 cup flour, yeast, grated orange rind and vital wheat gluten; mix well. In saucepan or microwave-safe dish, heat 1/3 cup water, vegetable oil and honey to 120-130°F. Add warm liquids and moistened cereal to flour mixture. Blend on low speed for 30 seconds; beat on medium speed for 4 minutes.
Switch to dough hook attachment. Gradually stir in enough remaining flour to make a firm dough. Knead until smooth and elastic, about 5 to 7 minutes.(NOTE: For hand mixing: following above steps, mix ingredients in large mixing bowl using a wooden spoon or dough whisk. Knead on floured surface until smooth and elastic.) Place dough in lightly oiled bowl and turn to grease top. Cover; let rise until indentation remains after poking dough with finger down to second knuckle.
Turn dough onto lightly floured surface; punch down to remove air bubbles. Shape into a round loaf. Place on greased or parchment paper lined cookie sheet. Cover; let rise in warm place until indentation remains after touching.
Preheat oven to 375°F.
With a very sharp knife, make 2 cuts to form an X, 1/4-inch deep, on top of loaf. Bake in for 30 to 40 minutes. Remove from cookie sheet; cool on rack.