The same Sri Lankan-inspired marinade that I use on meat works well for veggies too. Efficient. 
And as a bonus, the veggies don’t need marinating for any length of time — you can just coat them and grill.
Remember that veggies cook at different speeds, so if you’re mixing them on skewers, be careful about adjusting size of the pieces so they cook the optimal amount.
Of these, I thought the eggplant, mushroom, bell pepper and ripe jackfruit worked best. (You can grill eggplant and mushroom on skewers together, and bell pepper and ripe jackfruit on skewers together. Ripe jackfruit is delicate, so be sure to oil the grill well, and turn skewers with care.).
The green jackfruit and the zucchini didn’t have as much inherent flavor as the other vegetables, so they were a little boring — but tasty once dipped in the yogurt sauce! (I’d expect summer squash to behave the same way as zucchini.) All nice with toasted naan.
To make this vegan, just use vegan mayo and yogurt, and skip the Worcestershire sauce.
zest of 2 limes
4 large garlic cloves, finely grated
1 c. mayonnaise
1 c. plain whole-milk yogurt
3 T lime juice
1 t. salt
1/3 c. ketchup
1/4 c. Worcestershire sauce
2 t. Sri Lankan curry powder
1-2 t. cayenne
3 T vegetable oil (plus more for grill)
veggies of your choice, cut for skewers
naan bread
1. Make sauce: In a large bowl, whisk lime zest, garlic, mayonnaise, yogurt, and 2 t. of the lime juice in a large bowl to combine, add salt to taste. Transfer 1/2 c. of sauce to small bowl for serving; cover and chill until you’re reading to eat.
2. Make marinade: Whisk into the remaining sauce the ketchup, Worcestershire sauce, curry powder, cayenne, and remaining lime juice. Add veggies, toss to coat.
3. Prepare grill for medium-high heat; oil grate. While grill is heating, remove veggies from marinade, letting any extra drip back into the bowl; thread veggies onto metal skewers, spacing slightly apart.
4. Grill kebabs, turning a few times, until browned and cooked through, 6-10 minutes (varies depending on the vegetable, so keep an eye on them). Lightly toast pita on grill, and serve kebabs with reserved yogurt sauce.
Curry powder recipe here: https://serendibkitchen.com/sri-lankan-curry-powder/
