Preheat the oven to 375°F (190°C). Lightly grease a baking dish (11 ¾” x 7 ½” or similar size) with olive oil.
Arrange a single layer of squash slices at the bottom of the baking dish, slightly overlapping them (use about half the zucchini for this layer). Spread a generous layer of basil pesto (½ cup) evenly over the squash slices. Sprinkle half the amount of shredded mozzarella cheese and grated Parmesan cheese over the pesto layer.
Repeat the layers of squash, pesto, and cheese.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30-40 minutes, until zucchini are soft when pierced with a fork.
After 30-40 minutes, remove the foil and continue baking for an additional 5- 10 minutes, or until the cheese is golden and bubbly.
Once done, remove the squash Parmigiana from the oven and let it cool for a few minutes before serving.
