Grilled Beef Fajitas with Green Yogurt Sauce

Source: Rachel Ray

1 1/2 cups plain yogurt
Juice of 2 limes (1/3 cup)
2 tablespoons extra-virgin olive oil plus 1/4 cup for brushing vegetables
1 tablespoon hot pepper sauce
2 tablespoons chopped fresh thyme leaves, a few sprigs
1 (1 1/2 pound) sirloin steak or flank steak
2 red or green bell peppers, halved and seeds removed
1 large sweet onion, such as Vidalia, Maui or Texas Sweet
Salt and pepper, to taste
1 jalape