Sprinkle mozzarella cheese and crumbled feta cheese on top of flatbread. Top with tomatoes, roasted red bell pepper, kalamata olives, and minced garlic. Sprinkle with dried oregano, red pepper flakes; drizzle olive oil on top. Grill over indirect heat for 4-5 minutes until cheese is melted. Alternatively, bake in 425 oven until cheese is melted.
Place Greek Salad Dressing ingredients in a jar and cover; shake until blended.
Toss together baby greens, cucumber and onion and dress lightly with some Greek Salad Dressing.
Place tossed salad on top of pizza. Cut into serving pieces and serve.