Preheat the oven to 375°F (190°C). Arrange the mini pastry shells or pizza bases on a baking sheet lined with parchment paper.
Heat the olive oil in a skillet over medium heat. Add the chopped vegetables and cook, stirring occasionally, until they are tender and slightly caramelized, about 5-7 minutes. Season with salt, pepper, and oregano.
1 package Mini pastry shells or pizza bases
Combine the cooked vegetables with shredded cheese in a mixing bowl, mixing until evenly distributed.
1 package Mini pastry shells or pizza bases
Spoon a generous amount of the vegetable and cheese mixture onto each pastry shell, filling them generously but without overflowing.
1 package Mini pastry shells or pizza bases
Bake in the preheated oven for about 15-20 minutes, or until the pastry shells are golden brown and the cheese is bubbly and melted. You'll see the edges crisping and bubbling.
Remove from oven and let cool slightly before serving. Optionally, garnish with fresh herbs or additional salt and pepper.