Prepare a muffin tin with muffin cups and pre-heat the oven to 350 degrees F. In a large mixing bowl, stir together the first 5 ingredients: the flour, oats, cinnamon, nutmeg and salt. Remove 1/2 cup of the mixture and place in a small bowl. Set aside to make streusel.
To the large bowl, add the baking powder and baking soda and whisk to combine.
In a separate bowl, whisk together the oil, honey, eggs and yogurt. Make a well in the center of the dry mix in the large bowl, add the egg and honey mixture and whisk just until blended. Divide the batter among the prepared muffin cups.
To the small bowl of reserved oat mixture, add the butter and sugar, working it in with your fingers till it forms coarse crumbs. Sprinkle it evenly over the filled muffin cups, pressing the streusel gently into the batter so it adheres better while baking.
Bake for about 22 minutes, or until the muffins spring back when pressed gently with your finger. Cool for about 20 minutes and lift from the muffin tins with a small knife to prevent the streusel from falling off the muffins.
Serve warm, with butter and jam or preserves. Makes 12 muffins.
Recipe by Mani Naill