Now that summer is here, what are good, vegetarian/vegan picnic foods that withstand heat? As in won't go bad or melt.

Have you tried Amanda's Radish and Pecan grain salad
http://www.food52.com/recipes/9110_radish_and_pecan_grain_salad
Or the Parsley Thief's Warm Orzo Salad with Beets and Greens (omitting the cheese)
http://www.food52.com/recipes/7032_warm_orzo_salad_with_beets_greens

Both fantastic salads that are nice served at room temperature and can easily be vegan.

Kayb, tamales sound fantastic... and heat-proof. Thanks for the suggestion! I will get my Grandma's recipe.

I actually prefer the grain salads at room temperature. I think the taste is dulled by being too cold. And veg foods are far less in danger of spoiling than meats. Beans could be a problem, but acid ingredients will protect them, for limited periods of time. Don't leave food in a closed car or trunk. A cooler or cold pack when transporting is practical too.
When in doubt, last resort is peanut butter sandwiches.

Tamales. A great history of being a workingman's lunch, convenient to carry. Also, multi-grain salad; cook several different grains (bulghur, spelt, quinoa, wheatberries, millet, brown or wild rice, etc.), cool, mix, add dried fruit and a honey balsamic dressing. Good cold, better at room temp.

If you have time to do a lot of chopping: http://www.food52.com/recipes/10875_hellenic_chopped_and_sliced_salad

One of my (many) standbys for summer days is a refreshing cucumber salad:

2 (preferably seedless, but whatever you can get) cucumbers, peeled and sliced as fine as possible
1/2 a small white onion
1/4 cup white wine vinegar
sugar to taste

If you have a mandoline, this takes no more than 5 minutes to prepare and you just need to keep tasting for the vinegar/sugar mix depending on how much cucumber you use. You can slim down this recipe substantially for just one person. It can sit out for quite a while and still be delicious...it actually tastes better after a little time to marinate. Or this tofu (http://www.food52.com/recipes/11358_grilled_peanut_tofu) which is great cold or hot off the grill and which I have for lunch today myself :)

Thai Pasta Salad. Rice, Garbanzo and Artichoke salad, Tapenade. Ratatouille. Caponata. Salade Nicoise w/o the tuna. Lentil Salad.

The possibilities are endless!

roasted vegetables can hang out without a cooler. i do big batches of tomatoes, zucchini, eggplant, spring onions (or other), and peppers in the summer.

A side note: It's interesting that in history most of the dishes mentioned here. Were designed for 'workman' lunches..or traveler meals, in the age before refrigeration.
Hummus, Baba ganoush, Soba, tabouli, etc..etc. Even stuffed grape leaves.
We eat most of those 'cold' now...but originally, they were used because of their ability to transport well without cold.

Spring rolls or a rice noodle salad? I wrap my spring rolls in wet paper towels.

@anita

Most of the dishes posted here won't really be hurt by heat.
But take a look at insulated bento boxes. Such as "Mr Bento".
http://www.amazon.com/gp/product/B0016S7MJM/ref=pd_lpo_k2_dp_sr_2?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B001TI1MTU&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=15NQ2263VMZX5ZB4AECJ

and other insulated bento box options.

Tamarind rice.. Not sure if the recipe is around on Fodd52, but can give you leads if interested..

Yes indeed a quinoa tabouleh! Oh daughter (age 5) loves couscous and wanted it for her b-day party, we were out and I substituted quinoa for it with dried apricots, very green olives, toasted almonds, spring onions, cilantro, basil, olive oil and lemon juice.

These all sound scrumptious but I was thinking more along the lines of things you can carry around in the heat for hours before you eat them and flavor won't go off. Cold salads might not work.

@syonia: Quinoa tabooli!

I made that last week..it was fantastic. Yes, thumbs up!

@summer of eggplant. I was going for the same thing but got too verbose.

Still: The Kewpie product I mentioned is excellent for noodles, Goma Mae (sp) Spinich.
I used to make the dressing from scratch but that product is just right...the SO loves it and it's quick---but a bit pricey as the spinach really soaked it up. Still it tastes fantastic and makes him happy.

Quinoa tabooli! That's one of my favorites. There are lots of variations on the Italian Insalata di Risotto that are vegetarian. Both of those will stay good in heat for a few hours. Don't forget the good old-fashioned peasants' meal: bread or crackers, cheese, fresh veggies, and olive tapenade. Alright, so maybe peasants wouldn't have the tapenade; but you should.

A cold. Corn, black bean salad..with corn kernels, A can of black beans (rinsed). With a dressing of lime juice/olive oil, cumin. Cilantro (optional) or parsley and sliced green onions.

Lightly blanched asparagus with a vinaigrette.

Cold noodles (soba, buck wheat noodles) with a sesame seed dressing.
Cold spinach (blanched, drained and chilled) with sesame dressing.
(Kewpie makes a great bottled dressing..or make your own google Goma dressing).
http://1.bp.blogspot.com/-CltD4R3fi7E/TcM5HIKnRbI/AAAAAAAABKA/exfzg5KnOX0/s1600/Blogging+008+copy.jpg
Available in Asian stores.

Quick pickled cucumber slices: 1 part rice or apple cider vinegar, 1 part water, 1.3 part sugar (optional), a bit of salt, and peppercorns, 1/3 part pickled ginger--let sit at least 3 hours or overnight. (english cucumbers pealed/stripped..and sliced into disks).
(can be made into a seaweed salad with adding rehydrate wakeme seaweed).

Hummus or baba ganoush.

Sesame noodles. I would reference Frank Bruni's latest book.