Preheat oven to 400°F. Line baking sheet with aluminum foil and place bacon strips side-by-side in pan. Bake for 15 to 20 minutes, or until crispy. Transfer to paper-towel lined plate to cool.
While bacon is cooking, segment the oranges: First, cut the ends off each orange, then carefully cut off the rest of the rind. Next, with a very sharp medium knife, cut each segment out of its membrane, getting as close to the membrane as possible. You should end up with a pile of orange segments free of their fibrous membranes.
Carefully chop bacon while still warm, using a paper towel to protect fingers if necessary. Toss all salad ingredients together – the warm bacon should wilt the spinach slightly.
Assemble the dressing by mixing all the dressing ingredients in a jar and shaking well, until ingredients are emulsified. You can also whisk ingredients in a bowl.
Store salad dressing separately until ready to serve.