Season the Chicken - Evenly season both sides of each chicken breast with salt and pepper. Drizzle ½ teaspoon of olive oil on both sides, rubbing it onto the surface to coat evenly.
Grill the Chicken - Preheat the grill or grill pan over medium-high heat. Oil the grill grates. Place the chicken on the grill and close the lid if using a barbecue. Cook until the internal temperature reaches 160 to 165ºF (71 to 74ºC) on a meat thermometer, about 5 to 7 minutes per side, depending on thickness.
Slice the Chicken - Rest the chicken for 10 minutes. Cut into ¼-inch thick slices against the grain. Set aside.
Make the Dressing - In a blender, add sliced strawberries, balsamic vinegar, water, shallots, mustard, honey, salt, and pepper. Blend on high speed until smooth, about 10 seconds. With the blender running on medium-low speed, slowly add the olive oil in a thin stream until thickened—season with salt, pepper, and honey to taste.
Assemble the Salad - In a large serving bowl, add romaine, cucumber, strawberries, avocado, feta cheese, pecans, and red onion. Top with the sliced chicken.
To Serve - Drizzle some dressing on top of the salad or serve on the side.
Notes
Recipe Yield: About 10 cups salad and 1 ⅓ cups dressing.
Serving Size: About 1 ¼ cup salad plus 3 tablespoons salad dressing.
Storing: Store salad in an airtight container for up to 2 days. Dressing can be prepared 3 days in advance.