Wash and chop your vegetables. Rinse them under cold water, slice the onion, bell pepper, and zucchini into thin strips, cut the broccoli into small florets, and halve the cherry tomatoes.
Select a large skillet or frying pan for sautéing. A non-stick pan works best.
Pour in the olive oil and heat it over medium heat for about 1 minute until it shimmers.
Add the sliced onion to the hot oil and sauté for 3-4 minutes until translucent. Stir in the minced garlic and cook for another minute until fragrant.
Toss in the bell pepper, zucchini, and broccoli. Sauté for 5-7 minutes, stirring occasionally until tender yet still crisp.
Add the halved cherry tomatoes, dried oregano, salt, and black pepper. Cook for an additional 2-3 minutes until the tomatoes soften slightly.
If desired, drizzle balsamic vinegar over the vegetables, toss everything together, and remove from heat.