Heat a grill pan over medium-high heat. Brush corn ears with 1/2 tsp. of olive oil each. Place on the grill and lower heat to medium. Cook, turning regularly, until there are grill marks on all sides - approx. 10 minutes. Remove from heat and set aside for 3-5 minutes, or until cool enough to handle. Using a sharp knife, cut kernels off of the cob.
Add remaining 1 tsp. of olive oil to a pan over medium heat. Place bread slices in the pan and toast until both sides of each slice is browned.
To assemble, top each slice of toast with 1/2 an avocado, corn kernels, serrano pepper slices and cilantro. Drizzle with chimichurri sauce and top with salt and pepper.