What is a good side dish for french onion soup?

Foie Gras and cornichons. Remember there is already bread in the soup.

Slices of apple or pear. A definitely a crusty baguette.

Slices of apple or pear. A definitely a crusty baguette.

Onion soup with a crouton/cheese gratineed on top, with a green salad is a complete meal, I think. I'd use a tart vinaigrette to cut thru the cheesy richness, maybe toss in a few apple or pear slices if you want to dress it up - compliments the cheese too.

I don't normally serve anything with it other than some more bread to dip into the soup. But, I could see it going well with a roast.

Slices of chewy, airy crusty bread and as Trena mentioned a salad.

Not sure this classifies as a "side dish" but I love french onion soup with a croque madame or croque monsieur!

It's often seen as a meal itself. But/and was eaten as an early morning res torative after a long night of partying. Keeping that in mind, maybe serve mini sliders of deli meat or beautiful slow-cooked French scrambled eggs...high protein, easy, also restorative.