Whisk marinade mix, oil and 1/4 cup beer until blended; pour over vegetables.
Let stand 30 min. at room temperature to marinate.
Heat grill to medium heat.
Transfer vegetable mixture to skillet; cook and stir on medium-high heat 5 min. or until onions are golden brown. Cover; simmer on low heat 10 min., stirring occasionally. Meanwhile, bring remaining beer to boil in medium saucepan.
Add brats; cook 5 min.
Drain brats; grill 4 to 5 min. or until done (160F), turning occasionally.