Place cornbread mix in a 1-gallon resealable bag; season with salt and black pepper. Add squash, seal the bag, and shake until evenly coated. Remove squash from the bag and shake off any excess cornmeal.

Heat about 1/4 inch of olive oil in a large skillet over medium heat.

Working in batches, fry squash until the center is cooked and the edges are crisp, 2 to 3 minutes per side. Remove with a slotted spoon and drain on a paper towel-lined plate.