Preheat your oven to 375°F.
Prepare the vegetables: slice the zucchini, red bell pepper, and red onion. Halve the cherry tomatoes and roughly chop the spinach and mixed herbs.
In an oven-safe skillet, heat the olive oil over medium heat. Sauté the red onion for 2 minutes until slightly softened.
Add the zucchini, red bell pepper, and cherry tomatoes to the skillet, and cook for an additional 3-4 minutes until they begin to soften.
Stir in the spinach and fresh herbs, and cook until the spinach wilts.
In a bowl, whisk together the eggs. Pour the eggs evenly over the sautéed vegetables, allowing them to mix well.
Crumble the goat cheese evenly on top of the mixture.
Allow the frittata to cook on the stovetop for 2 minutes, then transfer the skillet to the oven.
Bake the frittata for 10-12 minutes, or until the eggs are set and slightly golden on the top.
Remove from oven, let it rest for a couple of minutes, slice, and serve warm.