Preheat the oven to 430℉ | 220℃.
In a large bowl, coat the pumpkin cubes with the olive oil, cumin, coriander, paprika and salt.
Spread the pumpkin on a baking sheet in a single layer and scatter the whole garlic cloves around (skins on). The garlic will help flavour the pumpkin while cooking and is a great addition to the salad.
Roast in the oven for about 30 minutes, until the pumpkin is tender and has a lightly browned, caramelised finish. You may need to toss them halfway through for an even finish. At this point, check the garlic, it needs to be squishy on the inside, not dry. This will take around 15-20 minutes of the cooking time. Remove the garlic if cooked and set aside to cool.
While the pumpkin is cooking, cook your quinoa. If you have not cooked quinoa before, the instructions will be on the packet. We have also included instructions in the recipe notes.
Lightly toast the walnuts in a dry non-stick pan - approximately 5 minutes on medium heat. Watch they don't blacken. Chop if you prefer roughly chopped over whole walnuts.
Once the pumpkin is cooked, place in your serving bowl and allow to cool. Drizzle any juices from the baking pan over the pumpkin at this point and squeeze your roasted garlic cloves from their skins and toss through the pumpkin.
When the pumpkin has cooled combine all ingredients except your greens - pumpkin, quinoa, onion and walnuts. Make sure all the ingredients are well combined to mix through the spices from the pumpkin.
Either just before you pack your salad for your picnic or when ready to serve, add the greens and lightly toss.
I find this salad does not need a dressing as the soft pumpkin with the full flavour of the spices gives it the moisture and flavour it needs. If you do feel you need a dressing, a light drizzle of olive oil will mix with the spices perfectly creating its own dressing. Or, if you have some, a little drizzle of walnut oil gives an excellent finish. Just go easy with both, so it doesn't make your salad sloppy.