For the Flank Steak, mix Marinade Mix and beer in small bowl. Reserve 2 tablespoons of the marinade. Place steak in large resealable plastic bag or glass dish. Add remaining marinade; turn to coat well. Refrigerate 30 minutes or up to 4 hours.
Massage steak and marinade in plastic bag for 5 minutes to infuse flavor faster.
Meanwhile, for the Chimichurri, mix cilantro, parsley, green onions, garlic, oil, vinegar, red pepper and salt in medium serving bowl until blended. Gently stir in 2 tablespoons of the blue cheese. Cover. Refrigerate until ready to serve.
Remove steak from marinade. Discard any remaining marinade.
Grill steak over medium-high heat 6 to 8 minutes per side or until desired doneness, brushing with reserved marinade during last few minutes of grilling. Let steak stand 5 minutes before slicing. Sprinkle remaining blue cheese over chimichurri sauce and serve with sliced steak.