Step 1

1 Have ready six large resealable food containers available and a grilling basket

Step 2

2 In a large bowl with a pouring spout, gently crush the thyme, rosemary and oregano with your hands to release their oils

Step 3

3 Add the garlic

Step 4

4 Worcestershire sauce, vinegar, oil, sugar, salt and pepper and whisk to combine

Step 5

5 Place the peppers in one of the containers, and put the other vegetables -- onion, squash, tomatoes, mushrooms and potatoes -- in separate containers

Step 6

6 Pour some of the marinade and herbs into each of the containers (add the marinade to the mushrooms just before grilling if you'd rather have them firm than soft)

Step 7

7 Add just enough marinade so the vegetables are well coated

Step 8

8 Seal and gently shake to coat evenly

Step 9

9 Let the vegetables marinate at room temperature for at least 30 minutes, giving them a gentle shake or turn after 15 minutes

Step 10

10 Do not marinade for longer than 1 hour

Step 11

11 If using a gas grill, preheat to medium-high, or around 350 degrees

Step 12

12 If using a charcoal grill, fill a chimney starter with charcoal, light it, and when the coals are red hot, dump them into your grill and distribute them evenly under the cooking area for direct heat

Step 13

13 Replace the cooking grate and use a grill thermometer or use the hand method: If you can hold your hand an inch from the grill for about six seconds, the grill should be around 350 degrees

Step 14

14 (If you're planning to cook batches of vegetables, it's a good idea to have another chimney of coals heating up while you cook, so you an replenish with hot coals as needed

Step 15

15 )

Step 16

16 Lightly coat a grill basket with nonstick spray

Step 17

17 Drain the marinade from each container and remove any large herb sprigs that may be stuck to the vegetables so they don't burn during grilling

Step 18

18 Add the vegetables, in turn, to the grill basket and grill separately, tossing once, to better control their doneness

Step 19

19 As each is done, transfer to a large serving platter

Step 20

20 If any vegetables start to stick, respray the grill pan with cooking spray between batches

Step 21

21 The peppers will need about 5 minutes and should have char marks but still be firm; same with the squash

Step 22

22 The onion requires 3 to 5 minutes and should be slightly charred

Step 23

23 The mushrooms and precooked potatoes each require about 3 minutes

Step 24

24 The tomatoes take 1 to 2 minutes, just until their skin blisters

Step 25

25 Sprinkle with chopped parsley, if using, and serve at room temperature, or reheat in a hot oven for a few minutes and then sprinkle with the parsley, if using