Zucchini, Summer Squash, Onion and Cheese Casserole

Wendy Hopper posted this on facebook.

Zucchini, Squash, Onion and Cheese Casserole

2-3 T Olive oil (plus tiny bit more for drizzling at the end)
1 medium onion, sliced thin
3 cloves garlic, finely diced
1 medium zucchini, ends cut off and thinly sliced into circles
1 medium summer squash, ends cut off and thinly sliced into circles
pinch of freshly grated nutmeg  (I used the non-fresh type)
2 cups shredded white cheddar cheese
1/2 cup Rosemary Asiago Cheese (or other cheese of choice)
1/3 +1/4 cup panko crumbs (I used regular bread crumbs
Grated Parmesan for dusting on top
Salt and pepper to taste
Fresh chopped Italian Parsley for garnish (optional) (did not have)

Heat olive oil in a large pan over medium heat, add garlic
and onion and saute up, stirring occasionally (careful not
to burn the garlic) until softened about 6-8 minutes.
Add zucchini and squash to the same pan and continue
cooking, stirring occasionally until softened, about 12 minutes.
Add  nutmeg, pinch of salt and pepper and
stir in well.
Remove from heat and place contents of the pan into a
 large bowl to let cool slightly. Preheat Oven 375

Preheat oven to 375.
Stir in your 2 1/2 cups cheese and 1/3 cup panko until
well combined.
Add contents of bowl to a glass casserole dish (8x8) At
 this point taste test for salt and pepper - add some only
 if needed.

sprinkle the top with the remaining panko and Parmesan cheese.
Drizzle with just a touch of olive oil.

Place in the oven and bake about 10 minutes or until is gets
 bubbly around the edges.

Turn on broiler and broil (keeping a close eye) an additional 3-4 minutes until slightly browned on top.

Remove from the oven and let sit about 10 minutes before serving.   It turned out a tad bit on the dry side, I think it needs a bit of liquid, but not sure what kind of liquid.