Zest and juice the lemon. You'll need 2 Tbsp juice and ½ tsp zest. Combine the lemon juice, lemon zest, olive oil, basil, Dijon, salt, pepper, and chopped parsley in a bowl or jar. Whisk the ingredients in a bowl, or close the jar and shake until combined. Set the vinaigrette aside.
Bring a large pot of water to a boil for the pasta. Add a couple large pinches of salt to the pasta water, then add the pasta. Continue to boil until the pasta is tender (about 7 minutes), then drain in a colander. Rinse the pasta briefly with cool water, then allow it to drain well.
While the pasta is cooking and draining, prepare the rest of the vegetables. Slice the corn kernels off the cobs, slice the grape tomatoes in half, dice the zucchini, finely dice the onion, and dice the avocado.
Once the pasta has drained well and cooled, add it to a large bowl with the prepared vegetables. Pour the dressing over top, then toss until everything is evenly combined and coated in dressing. Season with a pinch of salt to taste, then serve.