Mediterranean Vegetable Salad

2 tablespoons canola or soybean oil

2 tablespoons chopped fresh or 2 teaspoons dried oregano leaves

1/2 teaspoon sugar

1/2 teaspoon salt

1/2 teaspoon ground mustard

1/2 teaspoon pepper

2 cloves garlic, finely chopped

3 large tomatoes, sliced

2 large yellow bell peppers, sliced into thin rings

6 oz washed fresh spinach leaves (from 10-oz bag), stems removed (about 1 cup)

1/2 cup crumbled feta cheese (2 oz)

Kalamata olives, if desired