Make the seasoning: Stir together the salt, pepper, granulated garlic, onion powder, oregano, and red pepper flakes. Set aside 2 to 3 teaspoons and store the rest in an airtight jar.
Prep the chicken: Pound the chicken breasts to an even ¾-inch thickness. Pat dry, rub with olive oil, and season both sides with the grill seasoning.
Make the baste: Melt the butter with the olive oil in a small saucepan over medium-low heat. Add the garlic and shallot and cook 1 to 2 minutes until fragrant. Remove from heat and whisk in the lemon juice, vinegar, Dijon, basil, oregano, parsley, and salt.
Grill: Preheat the grill to medium-high (425–450°F) and oil the grates. Grill the chicken 5 to 7 minutes per side until it reaches 165°F.
Baste: Brush both sides of the chicken with the baste during the last 2 to 3 minutes of cooking.
Rest and serve: Rest the chicken for 5 minutes, then brush with remaining baste and serve.