Prep all vegetables: halve the grape tomatoes, cube the English cucumber, dice the bell pepper evenly, and slice the red onion into thin strips.
Make the lemon-oregano vinaigrette: in a mason jar combine red wine vinegar, lemon juice, Dijon, minced garlic, dried oregano, salt, black pepper, and olive oil. Shake well and let stand 10 minutes to mellow.
Divide about 2 tablespoons of dressing into the bottom of each of the 5 meal prep containers.
Layer cucumbers and bell peppers next; they handle contact with dressing best.
Add tomatoes, red onion, and Kalamata olives on top. Keep separated if your containers have compartments.
Crumble feta from a block and store it in a separate small container for each serving.
Label containers with the date, seal, and refrigerate.
To serve, add the feta, shake to distribute the dressing, and enjoy cold.