Preheat oven to 425°F.
Rinse and peel onion. Peel garlic. Rinse eggplant, zucchini, squash, and tomato.
Dice onion and eggplant into ½-inch pieces. Slice zucchini and squash into ½-inch slices. Chop tomato. Mince garlic.
In a medium bowl, add onion, eggplant, zucchini, squash, garlic, oil, basil, oregano, salt, and black pepper. Toss until veggies are well coated.
Coat baking sheet with non-stick cooking spray. Spread veggies out in a single layer so they do not touch. Bake for 20 minutes. Remove from oven.
Add tomato to baking sheet. Return baking sheet to oven. Bake, stirring occasionally, until veggies are golden crisp, about 15–20 minutes more.