In a large shallow sauté pan, heat 1 tablespoon olive oil over medium heat. Add sliced squash and zucchini to pan, cook until beginning to brown. Add garlic and sauté until fragrant, 30 seconds. Add corn and cook, stirring occasionally, until warmed through and slightly softened, 2 minutes or so. Add tomato and oregano; season to taste with salt and pepper.  Continue to sauté, tossing the ingredients together until fully incorporated and warm.