In a large bowl mix the oats, rye flour, brown sugar, salt, butter, cinnamon and nutmeg.
Pour boiling water over mixture, stir to combine.
Set aside to cool for about an hour.
Stir in the starter and then about 4 cups of flour.
Turn the dough out onto a floured board. Knead 5 to 8 minutes, kneading in as much of the remaining 1 cup flour as needed to keep the dough from sticking.
Place dough in a lightly greased bowl. Turn to coat top, then cover. Set in a warm place to rise until doubled about 3 to 4 hours. Gently punch down the dough and divide in half.
Shape into two loaves and place in 2 greased 9 x 5 inch pans.
Cover loosely and let rise in a warm place until doubled again. About 1 1/2 to 2 hours.
Bake at 350º for 40 to 45 minutes or until loaves are golden brown and sound hollow when tapped. Remove pans from oven. Remove bread from pans and cool on wire rack.
Brush tops of loaves with melted butter for a softer crust, if desired.