Preheat oven to 400°.
Unroll pizza dough; place on a baking sheet coated with cooking spray. Press into a 13 x 9-inch rectangle. Arrange bell pepper strips in a single layer over crust. Bake 19 minutes or until crust is lightly browned. Remove from oven and immediately sprinkle with feta cheese.
While crust is baking, combine olive oil and next 5 ingredients in a small bowl; stir with a whisk. Combine salad greens, tomatoes, and onion in a large bowl. Pour dressing over salad; toss gently.
Cut focaccia into 4 rectangles; top each focaccia rectangle evenly with greens. Serve immediately.