Bring a large pot of water to a boil. Add the corn, allow to return to boil. Remove from heat, cover, allow to sit for 10-15 minutes, until cooked. Remove from hot water and allow to cool.
Once cool enough to handle, use a knife to cut the corn kernels off of the cob.
In a large bowl, add the corn kernels, bell pepper, shallot, and basil. Stir to combine, then gently stir in the avocado.
In a mason jar, add the lemon juice, olive oil, garlic, salt and pepper. Shake until completely mixed. Pour over salad. Stir to fully coat everything with the dressing. Taste and season with more salt and pepper if desired. Can be served right away or made a day ahead of time. Keep in an airtight container in the fridge until ready to serve.