Preheat the oven - Preheat the oven to 375°F (190°C).

Prepare the vegetables - Wash the yellow squash, zucchini, red bell pepper, and cherry tomatoes. Trim the ends of the squash and zucchini, then cut them into thin slices. Remove the stem and seeds from the red bell pepper, and cut it into thin strips. Halve the cherry tomatoes.

Sauté the vegetables - Heat olive oil in a large skillet or pan over medium heat. Add the sliced yellow squash, zucchini, red bell pepper, and minced garlic to the pan. Sauté for 5-6 minutes until the vegetables are slightly softened. Stir occasionally to ensure even cooking.

Season and add tomatoes - Season the sautéed vegetables with salt and black pepper to taste. Add the halved cherry tomatoes and continue cooking for another 2-3 minutes until the tomatoes start to release their juices. Remove the skillet from heat.

Combine with basil - Transfer the sautéed vegetables and cherry tomatoes to a mixing bowl. Add the fresh basil leaves and gently toss to combine. The heat from the vegetables will slightly wilt the basil.

Assemble the casserole - Grease a baking dish with olive oil. Spread the sautéed vegetable mixture evenly in the baking dish.

Top with cheese and breadcrumbs - Sprinkle grated Parmesan cheese evenly over the vegetables. Then, top it off with breadcrumbs for a crispy texture.

Bake to golden perfection - Place the baking dish in the preheated oven and bake for 20-25 minutes, or until the casserole is golden brown and bubbly on top.

Serve and enjoy - Remove the casserole from the oven using oven mitts or kitchen gloves. Let it cool for a few minutes, then serve warm. This Sunshine Medley Squash Delight makes a perfect side dish or a satisfying vegetarian main course. Enjoy the vibrant flavors of summer!