Prepare the dressing by whisking together the mayonnaise, vinegar, honey, Dijon, salt, and some freshly cracked pepper (about 10 cranks of a pepper mill). Refrigerate the dressing until ready to use.
Slice the bacon into one-inch pieces. Cook the bacon in a skillet over medium heat until brown and crispy. Transfer the bacon to a paper towel lined plate to drain.
Chop the lettuce into bite-sized pieces, then rinse with cool water in a colander. Allow the lettuce to drain while you prepare the rest of the toppings.
Thinly slice the red onion. Slice the grapes in half. Crumble the feta.
To build the salads, divide the lettuce between four bowls and top each with grapes, sliced onion, bacon pieces, and crumbled feta. Drizzle the creamy Dijon dressing over top, then enjoy.