To make the salmon marinade, whisk together the olive oil, lemon juice, dill, oregano, minced garlic, salt, and pepper in a small bowl until well combined.
Place the salmon on a prepared baking sheet, then brush the marinade evenly over the top. Let it sit for 15-20 minutes to soak up the flavor before cooking.
Preheat your oven to 400°F. Once heated, place the salmon in the oven and bake for about 12 minutes, depending on the thickness, or until it reaches an internal temperature of 145°F.
To make the Greek vinaigrette, add the olive oil, red wine vinegar, lemon juice, minced garlic, mustard, and oregano to a small bowl or jar. Whisk or shake until well combined and emulsified, then season with salt and pepper to taste.
To assemble, add a base of mixed greens to a bowl, then layer on the sliced cucumber, chopped red onion, grape tomatoes, brown rice, goat cheese, avocado, kalamata olives, and cooked salmon. Drizzle with your homemade Greek vinaigrette and enjoy!