In a medium bowl, combine the marinade ingredients.
In a large bowl, combine half the marinade with the chicken breasts, chicken thighs, and shrimp. Toss to combine. Cover and let marinate for at least 1 hour. If marinating for longer than 1 hour, make sure to refrigerate.
Place a grill pan over medium-high heat or preheat a gas or charcoal grill. Brush the corn with reserved unused marinade and wrap in foil. Toss the mushrooms with 1/4 cup of the reserved unused marinade. Grill the chicken breasts and thighs to an internal temperature of 165 degrees F, about 7 minutes a side. Grill the corn inside the foil, for about 5 minutes a side. Grill the peppers for about 5 minutes a side. Grill the shrimp and the mushrooms, about 2 minutes a side. Brush the grilled peppers with the last of the reserved unused marinade. Slice the peppers and mushrooms before serving, if desired.
Arrange grilled meats and vegetables over the saffron orzo on a large platter and serve immediately.
In a large pot, bring the chicken stock to a boil over high heat. Reduce the heat to low, bringing the stock to a simmer. Add the saffron, stir, and allow the saffron to bloom, about 5 minutes. Return the heat to medium and the stock to a boil, then add the orzo and cook until tender but still firm to the bite, stirring occasionally, about 8 to 10 minutes. Drain orzo and transfer to a large bowl. Add the olive oil, lemon juice, salt, pepper, and parsley. Toss to combine.