Place bacon on a microwave-safe rack or a plate lined with paper towels. Cover with paper towels. Microcook on 100 percent power (high) for 4 to 5 minutes or until bacon is crisp. Break up bacon and set aside.
In a microwave-safe 1-1/2-quart bowl or casserole, combine tomatoes, vinaigrette, and onion. Cover and microcook on high for 3 minutes or until mixture is hot.
Place greens in a salad bowl. Top with hot tomato mixture, bagel chips or croutons and bacon. Toss and serve immediately. Makes 4 side-dish servings.