Preheat the oven to 400°F.
Pat the chickpeas dry with a paper towel, toss with a pinch of salt, and roast on a baking sheet for 20 minutes until they are golden and crunchy.
Season the chicken breast with salt, pepper, and dried oregano.
Grill the chicken over medium-high heat for approximately 6 to 7 minutes per side until the internal temperature reaches 165°F.
In a small jar or bowl, whisk together the olive oil, lemon juice, and Dijon mustard to create the vinaigrette.
Slice the grilled chicken into thin strips.
In a large salad bowl, combine the mixed greens, sliced cucumber, and halved cherry tomatoes.
Top the salad with the warm grilled chicken and the roasted chickpeas.
Drizzle the lemon vinaigrette over the top and serve immediately.